Represent date from long, starting from year 0 instead of 1970 [duplicate] - java

This question already has an answer here:
How to calculate difference between two dates in years...etc with Joda-Time
(1 answer)
Closed 8 years ago.
I have a long-variable which represents an amount of delay in milliseconds. I want to transform this long to some kind of Date where it says how many hours, minutes, seconds, days, months, years have passed.
When using Date toString() from Java, as in new Date(5).toString, it says 5 milliseconds have passed from 1970. I need it to say 5 milliseconds have passed, and 0 minutes, hours, ..., years.


you cannot get direct values , without any reference date for your requirements, you need define first reference value like below:
String dateStart = "01/14/2012 09:29:58";
SimpleDateFormat format = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss")
Date d1 = format.parse(dateStart);
the above is your reference date , now you need to find the current date and time using following.
long currentDateTime = System.currentTimeMillis();
Date currentDate = new Date(currentDateTime);
Date d2.format(currentDate)
and the difference of these values like long diff=d2-d1 will gives values in milliseconds.
then
long diffSeconds = diff / 1000 % 60;
long diffMinutes = diff / (60 * 1000) % 60;
long diffHours = diff / (60 * 60 * 1000) % 24;
long diffDays = diff / (24 * 60 * 60 * 1000);
and similarly for months and years.
you can also refer the example given on this link for more information http://javarevisited.blogspot.in/2012/12/how-to-convert-millisecond-to-date-in-java-example.html


From what I understand from your question you could achieve your goal by writing a method that will suit your needs i.e.:
static public String dateFromMili (long miliseconds) {
// constants that will hold the number of miliseconds
// in a given time unit (year, month etc.)
final int YEAR_IN_MILISECONDS = 12*30*24*60*60*1000;
final int MONTH_IN_MILISECONDS = 30*24*60*60*1000;
final int DAY_IN_MILISECONDS = 24*60*60*1000;
final int HOUR_IN_MILISECONDS = 60*60*1000;
final int MINUTE_IN_MILISECONDS = 60*1000;
final int SECONDS_IN_MILISECONDS = 1000;
// now use those constants to return an appropriate string.
return miliseconds +" miliseconds, "
+miliseconds/SECONDS_IN_MILISECONDS+" seconds, "
+miliseconds/MINUTE_IN_MILISECONDS+" minutes, "
+miliseconds/HOUR_IN_MILISECONDS+" hours, "
+miliseconds/DAY_IN_MILISECONDS+" days, "
+miliseconds/MONTH_IN_MILISECONDS+" months, "
+miliseconds/YEAR_IN_MILISECONDS+" years have passed";
}
Than you will have to pas the number of miliseconds as a parameter to your new function that will return the desired String (i.e for two seconds):
dateFromMili (2000);
You could also print your answer:
System.out.println(dateFromMili(2000));
The result would look like this:
2000 miliseconds, 2 seconds, 0 minutes, 0 hours, 0 days, 0 months, 0 years have passed
Note that this method will return Strings with integer value (you will not get for example "2.222333 years" but "2 years"). Furthermore, it could be perfected by changing the noun from plural to singular, when the context is appropriate ("months" to "month").
I hope my answer helped.


This is how I solved the problem:
I used a library called Joda-Time (http://www.joda.org/joda-time/) (credits to Keppil!)
Joda-Time has various data-structures for Date and Time. You can represent a date and time by a DateTime-object.
To represent the delay I was looking for, I had two options: a Period data-structure or a Duration data-structure. A good explanation of the difference between those two can be found here: Joda-Time: what's the difference between Period, Interval and Duration? .
I thus used a Duration-object, based on the current date of my DateTime-object. It has all the methods to convert the amount of milliseconds to years, months, weeks, days, hours, minutes and seconds.

Related

How to calculate relative time spans using Java (code converting problem)? [duplicate]

This question already has answers here:
Java 8: Difference between two LocalDateTime in multiple units
(11 answers)
Closed 2 years ago.
I decided to give myself a challenge on Java that implements this question's achievement.
The things I have to do is get LocalDateTime, convert the same code from the linked question's answers, then receiving a string from the function.
Here's what I've done so far:
public static String relTime(LocalDateTime now)
{
// accepted answer converted to Java
const int min = 60 * SECOND;
const int hour = 60 * MINUTE;
const int day = 24 * HOUR;
const int mon = 30 * DAY;
// still don't know how to convert this method
var ts = new TimeSpan(DateTime.UtcNow.Ticks - yourDate.Ticks);
double delta = Math.Abs(ts.TotalSeconds);
if (delta < 1 * MINUTE)
return ts.Seconds == 1 ? "one second ago" : ts.Seconds + " seconds ago";
if (delta < 2 * MINUTE)
return "a minute ago";
if (delta < 45 * MINUTE)
return ts.Minutes + " minutes ago";
if (delta < 90 * MINUTE)
return "an hour ago";
if (delta < 24 * HOUR)
return ts.Hours + " hours ago";
if (delta < 48 * HOUR)
return "yesterday";
if (delta < 30 * DAY)
return ts.Days + " days ago";
if (delta < 12 * MONTH)
{
int months = Convert.ToInt32(Math.Floor((double)ts.Days / 30));
return months <= 1 ? "one month ago" : months + " months ago";
}
else
{
int years = Convert.ToInt32(Math.Floor((double)ts.Days / 365));
return years <= 1 ? "one year ago" : years + " years ago";
}
}
The only problem that I should encounter is from var ts = new TimeSpan(DateTime.UtcNow.Ticks - yourDate.Ticks);.
Although I read 2 questions from Stack Overflow finding equivalents of TimeSpan and Ticks, I baely have any ideas how to properly convert the line of code. Also, I have to get a double which will need math.abs() to get TotalSeconds which I can't really find a proper way to deal with either, but I did find ZoneOffset.ofTotalSeconds and still don't know how to deal with it.
So how can I convert this properly?
var ts = new TimeSpan(DateTime.UtcNow.Ticks - yourDate.Ticks);
double delta = Math.Abs(ts.TotalSeconds);

You need to gain a deeper understanding of what this method actually does. Literally translating code from C# to Java won't give you a good solution and gets you stuck on language-specific details.
The two lines basically calculate the (absolute) difference in seconds of a timestamp to the current time. This can be written in Java as follows:
Duration duration = Duration.between(LocalDateTime.now(), timestamp);
long delta = duration.abs().getSeconds();
I'm just addressing your actual question here on how to transform these two lines. The provided snippet is not valid Java code and some parts are missing. delta is the difference in seconds which does not necessarily need to be a double. The argument you pass to your method should be named anything else than now because this is the timestamp you want to compare to the current time inside the method.

You could use SimpleDateFormat to create a nice display format (use something like "HH hours, mm minutes and ss seconds ago" for the format (not sure if this exact example works)). You could also use Instant to get the current time, and you can use Instant.now().minusSeconds(Instant.now().minusSeconds(seconds).getEpochSeconds()) for the time difference (or just use System.currentTimeMillis() and multiply by 1000).
Alternatively, you could use Duration and write a custom display format using getSeconds() and getHours() etc.

LocalTime Military Time Parsing 00:00 [duplicate]

This question already has answers here:
LocalTime() difference between two times
(2 answers)
Closed 3 years ago.
I've looked at just about all the other posts pertaining to my question without finding a similar issue as mine.
I'm trying to get the time between two fields using this code.
LocalTime timeFrom = LocalTime.parse("16:00");
LocalTime timeTo = LocalTime.parse("00:00");
System.out.println(Duration.between(timeFrom,timeTo).toHours());
The issue I'm having is that the print out is negative 16 hours. What I want to accomplish is to get the amount of time from 4pm (which is 1600) to 12am (which is 00:00).
The result that I'm looking for would be 8 hours.
I have an idea of taking 1 minute from the 00:00, then getting the duration between those then just simply adding the 1 minute back to it, but I was thinking there must be an easier way.

After pondering I feel like I was looking for a programmer solution instead of a simple one...
The answer to this is just adding 24 hours back to the negative result!
LocalTime timeFrom = LocalTime.parse("16:00");
LocalTime timeTo = LocalTime.parse("00:00");
long elapsedMinutes = Duration.between(timeFrom, timeTo).toMinutes();
//at this point Duration for hours is -16.
//checking condition
if(timeTo.toString().equalsIgnoreCase("00:00")){
//condition met, adding 24 hours(converting to minutes)
elapsedMinutes += (24 * 60);
}
long elapsedHours = elapsedMinutes / 60;
long excessMinutes = elapsedMinutes % 60;
System.out.println("Hours: " + elapsedHours);
System.out.println("Minutes: " + excessMinutes);

I propose to check if the result is negative, then you don't limit the code to check for exact string equality, and 00:01 will still come out 8 hours:
import java.time.Duration;
import java.time.LocalTime;
public class StackOverflowTest {
public static void main(String[] args) {
String from = "16:00";
String to = "00:01";
LocalTime timeFrom = LocalTime.parse(from);
LocalTime timeTo = LocalTime.parse(to);
Duration duration = Duration.between(timeFrom,timeTo);
if (duration.isNegative()) duration = duration.plusDays(1);
System.out.println(duration.toHours());
}
/*
Prints:
8
*/
}
Or perhaps or more reader-friendly option:
...snip
Duration duration;
if (timeFrom.isBefore(timeTo)) {
duration = Duration.between(timeFrom,timeTo);
} else {
duration = Duration.between(timeFrom,timeTo).plusDays(1);
}

How to transfer Date.getTime() to hours and calculating difference

I have a program that is intaking an "AM" "PM" time and calculating out the hours in the day equivalent (in 24 hour format). For some reason it parses and calculates the time I input to the incorrect 24 hour equivalent (ie 5:00 pm comes to equal 22)
System.out.print("Enter the end time (HH:MM am): ");
endTime = input.nextLine();
Date ETime = time_to_date.parse(endTime);
Class method
public int get_Family_A_Calulation(Date STime, Date ETime) {
Date startTimeCalc = STime, endTimeCalc = ETime;
int pay = 0, hoursWorked, StartHour, EndHour;
StartHour = ((((int) startTimeCalc.getTime()) / 1000) / 60) / 60;
EndHour = ((((int) endTimeCalc.getTime()) / 1000) / 60) / 60;
pay = hoursWorked * 15;
return pay;
}
I am not sure where my error is can anyone give me advice on how to correct this error?

Use the latest classes available fron java8
LocalDateTime now = LocalDateTime.now();
System.out.println(now.getHour());

The actual data behind Date is milliseconds since the epoch. Any hour or time representation is based on the calendar date portion and takes into account timezone and daylight savings.
Regardless of what you do, there will be calculation issues across days, etc.
As suggested by Scary Wombat, use the new classes in java.time package. For your specific case, you need a LocalTime as the code is trying to represent a time element (hours, minutes, seconds, etc) without consideration for Date, TimeZone, etc.
https://docs.oracle.com/javase/8/docs/api/java/time/LocalTime.html

How to countdown to a date in java? [duplicate]

This question already has answers here:
Timer - counting down and displaying result in specific format [duplicate]
(2 answers)
Closed 6 years ago.
So i am creating an application to countdown to a date in java.
So lets say i parse these 2 days:
Date Now = 2016/01/15 16:52:22
Date End = 2016/01/15 18:37:18
How would i calculate the differences so that i can get the output like so:
1 hour, 44 minutes and 56 seconds
instead of the total hours, total minutes and total seconds.
I guess the best way to explain it is that i need to get the seconds left of the minute, the minutes left of the hour, etc, etc.

You haven't specify your date format. Supposed you use the Date class, the following code gives you a difference in milliseconds.
long difference = dateEnd.getTime() - dateNow.getTime();
Then you approach to your result with a simple calculation:
int seconds = (int) (difference / 1000) % 60 ;
int minutes = (int) ((difference / (1000*60)) % 60);
int hours = (int) ((difference / (1000*60*60)) % 24);

milliseconds to days

i did some research, but still can't find how to get the days... Here is what I got:
int seconds = (int) (milliseconds / 1000) % 60 ;
int minutes = (int) ((milliseconds / (1000*60)) % 60);
int hours = (int) ((milliseconds / (1000*60*60)) % 24);
int days = ????? ;
Please help, I suck at math, thank's.

For simple cases like this, TimeUnit should be used. TimeUnit usage is a bit more explicit about what is being represented and is also much easier to read and write when compared to doing all of the arithmetic calculations explicitly. For example, to calculate the number days from milliseconds, the following statement would work:
long days = TimeUnit.MILLISECONDS.toDays(milliseconds);
For cases more advanced, where more finely grained durations need to be represented in the context of working with time, an all encompassing and modern date/time API should be used. For JDK8+, java.time is now included (here are the tutorials and javadocs). For earlier versions of Java joda-time is a solid alternative.

If you don't have another time interval bigger than days:
int days = (int) (milliseconds / (1000*60*60*24));
If you have weeks too:
int days = (int) ((milliseconds / (1000*60*60*24)) % 7);
int weeks = (int) (milliseconds / (1000*60*60*24*7));
It's probably best to avoid using months and years if possible, as they don't have a well-defined fixed length. Strictly speaking neither do days: daylight saving means that days can have a length that is not 24 hours.

Go for TImeUnit in java
In order to import use, java.util.concurrent.TimeUnit
long millisec=System.currentTimeMillis();
long seconds=TimeUnit.MILLISECONDS.toSeconds(millisec);
long minutes=TimeUnit.MILLISECONDS.toMinutes(millisec);
long hours=TimeUnit.MILLISECONDS.toMinutes(millisec);
long days=TimeUnit.MILLISECONDS.toDays(millisec);

java.time
You can use java.time.Duration which is modelled on ISO-8601 standards and was introduced with Java-8 as part of JSR-310 implementation. With Java-9 some more convenient methods were introduced.
Demo:
import java.time.Duration;
public class Main {
public static void main(String[] args) {
// Duration between the two instants
Duration duration = Duration.ofMillis(1234567890L);
// Print Duration#toString
System.out.println(duration);
// Custom format
// ####################################Java-8####################################
String formattedElapsedTime = String.format(
"%d Day %02d Hour %02d Minute %02d Second %d Millisecond (%d Nanosecond)", duration.toDays(),
duration.toHours() % 24, duration.toMinutes() % 60, duration.toSeconds() % 60,
duration.toMillis() % 1000, duration.toNanos() % 1000000000L);
System.out.println(formattedElapsedTime);
// ##############################################################################
// ####################################Java-9####################################
formattedElapsedTime = String.format("%d Day %02d Hour %02d Minute %02d Second %d Millisecond (%d Nanosecond)",
duration.toDaysPart(), duration.toHoursPart(), duration.toMinutesPart(), duration.toSecondsPart(),
duration.toMillisPart(), duration.toNanosPart());
System.out.println(formattedElapsedTime);
// ##############################################################################
}
}
A sample run:
PT342H56M7.89S
14 Day 06 Hour 56 Minute 07 Second 890 Millisecond (890000000 Nanosecond)
14 Day 06 Hour 56 Minute 07 Second 890 Millisecond (890000000 Nanosecond)
Learn more about the modern date-time API from Trail: Date Time.

int days = (int) (milliseconds / 86 400 000 )

public static final long SECOND_IN_MILLIS = 1000;
public static final long MINUTE_IN_MILLIS = SECOND_IN_MILLIS * 60;
public static final long HOUR_IN_MILLIS = MINUTE_IN_MILLIS * 60;
public static final long DAY_IN_MILLIS = HOUR_IN_MILLIS * 24;
public static final long WEEK_IN_MILLIS = DAY_IN_MILLIS * 7;
You could cast int but I would recommend using long.

You can’t. Sorry. Or more precisely: you can if you know a time zone and a start time (or end time). A day may have a length of 23, 24 or 25 hours or some other length. So there isn’t any sure-fire formula for converting from milliseconds to days. So while you can safely rely on 1000 milliseconds in a second, 60 seconds in a minute (reservation below) and 60 minutes in an hour, the conversion to days needs more context in order to be sure and accurate.
Reservation: In real life a minute is occasionally 61 seconds because of a leap second. Not in Java. Java always counts a minute as 60 seconds because common computer clocks don’t know leap seconds. Common operating systems and Java itself do know not only summer time (DST) but also many other timeline anomalies that cause a day to be shorter or longer than 24 hours.
To demonstrate. I am writing this on March 29, 2021, the day after my time zone, Europe/Copenhagen, and the rest of the EU switched to summer time.
ZoneId myTimeZone = ZoneId.of("Europe/Copenhagen");
ZonedDateTime now = ZonedDateTime.now(myTimeZone);
ZonedDateTime twoDaysAgo = now.minusDays(2);
ZonedDateTime inTwoDays = now.plusDays(2);
System.out.println(ChronoUnit.MILLIS.between(twoDaysAgo, now));
System.out.println(ChronoUnit.MILLIS.between(now, inTwoDays));
Output:
169200000
172800000
So how many milliseconds are in two days depends on which two days you mean. And in which time zone.
So what to do?
If for your purpose you can safely define a day as 24 hours always, for example because your days are counted in UTC or your users are fine with the inaccuracy, use either Duration or TimeUnit. Since Java 9 the Duration class will additionally tell you how many hours, minutes and seconds there are in addition to the whole days. See the answer by Arvind Kumar Avinash. For the TimeUnit enum see the answers by whaley and Dev Parzival. In any case the good news is that it doesn’t matter if you suck at math because the math is taken care of for you.
If you know a time zone and a starting point, use ZonedDateTime and ChronoUnit.DAYS. In this case too the math is taken care of for you.
ZonedDateTime start = LocalDate.of(2021, Month.MARCH, 28).atStartOfDay(myTimeZone);
long millisToConvert = 170_000_000;
ZonedDateTime end = start.plus(millisToConvert, ChronoUnit.MILLIS);
long days = ChronoUnit.DAYS.between(start, end);
System.out.format("%d days%n", days);
2 days
If you additionally want the hours, minutes and seconds:
Duration remainingTime = Duration.between(start.plusDays(days), end);
System.out.format(" - and an additional %s hours %d minutes %d seconds%n",
remainingTime.toHours(),
remainingTime.toMinutesPart(),
remainingTime.toSecondsPart());
- and an additional 0 hours 13 minutes 20 seconds
If instead you had got an endpoint, subtract your milliseconds from the endpoint using the minus method (instead of the plus method used in the above code) to get the start point.
Under no circumstances do the math yourself as in the question and in the currently accepted answer. It’s error-prone and results in code that is hard to read. And if your reader sucks at math, he or she can spend much precious developer time trying to verify that you have done it correctly. Leave the math to proven library methods, and it will be much easier for your reader to trust that your code is correct.

In case you solve a more complex task of logging execution statistics in your code:
public void logExecutionMillis(LocalDateTime start, String callerMethodName) {
LocalDateTime end = getNow();
long difference = Duration.between(start, end).toMillis();
Logger logger = LoggerFactory.getLogger(ProfilerInterceptor.class);
long millisInDay = 1000 * 60 * 60 * 24;
long millisInHour = 1000 * 60 * 60;
long millisInMinute = 1000 * 60;
long millisInSecond = 1000;
long days = difference / millisInDay;
long daysDivisionResidueMillis = difference - days * millisInDay;
long hours = daysDivisionResidueMillis / millisInHour;
long hoursDivisionResidueMillis = daysDivisionResidueMillis - hours * millisInHour;
long minutes = hoursDivisionResidueMillis / millisInMinute;
long minutesDivisionResidueMillis = hoursDivisionResidueMillis - minutes * millisInMinute;
long seconds = minutesDivisionResidueMillis / millisInSecond;
long secondsDivisionResidueMillis = minutesDivisionResidueMillis - seconds * millisInSecond;
logger.info(
"\n************************************************************************\n"
+ callerMethodName
+ "() - "
+ difference
+ " millis ("
+ days
+ " d. "
+ hours
+ " h. "
+ minutes
+ " min. "
+ seconds
+ " sec."
+ secondsDivisionResidueMillis
+ " millis).");
}
P.S. Logger can be replaced with simple System.out.println() if you like.

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