I have two string variables for timer i.e.
String StartTimer1 = "00:00:00";
String EndTimer2 = "23:59:59";
Now , I need to calculate the time left from the present time (lets say if it is 05: 30:00) once the timer has started and time left has to be in milliseconds.
Here some tipps to get started:
You can parse the String to a Java Date like this:
SimpleDateFormat format = new SimpleDateFormat("HH:mm:ss");
Date startTimer1Date = format.parse(StartTimer1);
You can get the current Date and Time like this:
Date dateNow = new Date();
And since you are working with time only (and not with date and time), you will need to manipulate the Date, Month and Year of all values to a common base, e.g. :
Calendar c = Calendar.getInstance();
c.setTime(dateNow);
c.set(Calendar.YEAR, 1970);
c.set(Calendar.DAY_OF_YEAR, 1);
dateNow = c.getTime();
Related
I get a string in the format yyyy-MM-dd HH:mm which represents a Date and Time in UTC.
Next step is to put this into a Calendar (with TimeZone UTC).
In addition need to also create a separate Calendar which has converted the UTC to "Europe/London" timeZone (GMT/BST).
After that I need to be able to detect if the "Europe/London" calendar has a DST (Day Light Savings Offset).
The code below will show you how far I have got and it runs ok on a UK based computer whose default System Timezone is GMT. However when I run it on a pc whose timezone is UTC it fails. It seems to not be able to tell me if there is an DST_offset (its always zero).
Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
cal.set(Calendar.YEAR, 2016);
cal.set(Calendar.MONTH, 1);
cal.set(Calendar.DAY_OF_MONTH, 27);
cal.set(Calendar.HOUR_OF_DAY, 23);
cal.set(Calendar.MINUTE, 35);
cal.set(Calendar.SECOND, 0);
cal.set(Calendar.MILLISECOND, 0);
//This is required as Java Date JAN starts at 0.
int MonthCon = cal.get(Calendar.MONTH)-1;
cal.set(Calendar.MONTH, MonthCon);
Date d = cal.getTime();
SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssz");
f.setTimeZone(TimeZone.getTimeZone("UTC"));
System.out.println("UTC: " + f.format(d));
f.setTimeZone(TimeZone.getTimeZone("Europe/London"));
System.out.println("BST: " + f.format(d));
//Creates a BST calendar of the same UTC time
String dateStrBST = f.format(d);
SimpleDateFormat curFormater = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssz");
curFormater.setTimeZone(TimeZone.getTimeZone("Europe/London"));
Date dateObjBST = curFormater.parse(dateStrBST);
System.out.println("BSTNewDate: " + f.format(dateObjBST));
Calendar calBST = Calendar.getInstance(TimeZone.getTimeZone("BST"));
calBST.setTime(dateObjBST);
System.out.println("Current TimeZone is : " + calBST.getTimeZone());
int offset = calBST.get(Calendar.DST_OFFSET);
System.out.println("Day Light Savings: "+offset);
System.out.println("Transition Day: "+isDSTTransitionDay(cal.get(Calendar.YEAR),cal.get(Calendar.MONTH),cal.get(Calendar.DAY_OF_MONTH))+" Transition Type: "+DSTtransitionType(cal.get(Calendar.YEAR),cal.get(Calendar.MONTH),cal.get(Calendar.DAY_OF_MONTH)));
Unfortunately I need to be able to detect if any particular day is a transition day, that is to say a day that changes from DST on/off or off/on. Again this works on the local computer but not on the UTC timezone one.
private static boolean isDSTTransitionDay(int year, int month, int day) throws ParseException
{
Calendar calStartofDay = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calStartofDay.set(Calendar.YEAR, year);
calStartofDay.set(Calendar.MONTH, month);
calStartofDay.set(Calendar.DAY_OF_MONTH, day);
calStartofDay.set(Calendar.HOUR_OF_DAY, 00);
calStartofDay.set(Calendar.MINUTE, 0);
calStartofDay.set(Calendar.SECOND, 1);
Date dStartofDay = calStartofDay.getTime();
SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssz");
f.setTimeZone(TimeZone.getTimeZone("Europe/London"));
String dateStrUTCtoBST = f.format(dStartofDay);
SimpleDateFormat curFormater = new SimpleDateFormat("yyyy-MM-dd HH:mm:ssz");
curFormater.setTimeZone(TimeZone.getTimeZone("Europe/London"));
Date dateObjBST = curFormater.parse(dateStrUTCtoBST);
Calendar calBST = Calendar.getInstance();
calBST.setTime(dateObjBST);
int offsetStart = calBST.get(Calendar.DST_OFFSET);
calBST.add(Calendar.HOUR_OF_DAY, 23);
int offsetEnd = calBST.get(Calendar.DST_OFFSET);
//System.out.println("Start: "+offsetStart+" End: "+offsetEnd);
if (offsetEnd == offsetStart)
{
return false;
}else
{
//if(offsetStart<offsetEnd) {System.out.println("Transition to BST");}else{System.out.println("Transition to UTC/GMT");};
return true;
}
}
So on the UTC computer it fails miserably as it always puts Calendar.DST_OFFSET at zero. I have clearly misunderstood something along the way so any help/clarity would be good.
I pretty much have to keep Calendars as the rest of the code uses it but I realise the Java8 has many more fancy ways to do things.
Please allow me to be honest, I tried to read your code and didn’t really understand your way of trying to obtain what you want. If you can use Java 8, I recommend switching to using the Java 8 date and time classes. With these your job isn’t very complicated. For the demonstration I have chosen last October 30, the date when Britain (and EU) changed back from summer time (daylight saving time) to standard time.
String originalDate = "2016-10-30 23:35";
LocalDateTime localTime = LocalDateTime.parse(originalDate, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm"));
ZonedDateTime utcTime = localTime.atZone(ZoneOffset.UTC);
ZonedDateTime bstTime = utcTime.withZoneSameInstant(ZoneId.of("Europe/London"));
// the summer time offset is how many milliseconds?
long dstOffset = ChronoUnit.MILLIS.between(utcTime.toLocalDateTime(), bstTime.toLocalDateTime());
System.out.println(dstOffset); // prints 0
// try the same at start of day (midnight)
utcTime = utcTime.toLocalDate().atStartOfDay(ZoneOffset.UTC);
bstTime = utcTime.withZoneSameInstant(ZoneId.of("Europe/London"));
dstOffset = ChronoUnit.MILLIS.between(utcTime.toLocalDateTime(), bstTime.toLocalDateTime());
System.out.println(dstOffset); // prints 3600000
// and next midnight
utcTime = utcTime.plusDays(1);
bstTime = utcTime.withZoneSameInstant(ZoneId.of("Europe/London"));
dstOffset = ChronoUnit.MILLIS.between(utcTime.toLocalDateTime(), bstTime.toLocalDateTime());
System.out.println(dstOffset); // prints 0
You are using
Calendar calBST = Calendar.getInstance();
That sets calBST to the computer's timezone (on the UTC computer, it will be UTC).
calBST.setTime(dateObjBST); sets the time, not the timezone.
Try using getInstance(TimeZone zone) there also.
In any case, I would replace your code like this:
Calendar calStartofDay = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calStartofDay.set(Calendar.YEAR, 2017);
calStartofDay.set(Calendar.MONTH, 0);
calStartofDay.set(Calendar.DAY_OF_MONTH, 21);
calStartofDay.set(Calendar.HOUR_OF_DAY, 00);
calStartofDay.set(Calendar.MINUTE, 0);
calStartofDay.set(Calendar.SECOND, 1);
Calendar calBST = Calendar.getInstance(TimeZone.getTimeZone("Europe/London"));
calBST.setTimeInMillis(calStartofDay.getTimeInMillis());
// use this to check the time
System.out.printf("%tc%n", calBST);
Also, from the Calendar docs, be careful about this:
set(f, value) changes calendar field f to value. In addition, it sets
an internal member variable to indicate that calendar field f has been
changed. Although calendar field f is changed immediately, the
calendar's time value in milliseconds is not recomputed until the next
call to get(), getTime(), getTimeInMillis(), add(), or roll() is made.
Thus, multiple calls to set() do not trigger multiple, unnecessary
computations. As a result of changing a calendar field using set(),
other calendar fields may also change, depending on the calendar
field, the calendar field value, and the calendar system. In addition,
get(f) will not necessarily return value set by the call to the set
method after the calendar fields have been recomputed. The specifics
are determined by the concrete calendar class.
I have a date stored in a String field in SQLITE with the String value
"/Date(1411472160000+0100)/"
how can I convert this back into a date format , the code below doesn't work. I think I need to convert from the milliseconds first but I cant see how to even get the above text into a long format first ?
any suggestions ?
Date convertedDate = new Date();
SimpleDateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy HH:mm",
java.util.Locale.getDefault());
convertedDate = dateFormat.parse(dateString);
return dateFormat.format(convertedDate);
Well, a substring from the indexOf("(") to the indexOf("+") and you should find the date in milli.
From there, I believe you can find the date ;)
String s = "/Date(1411472160000+0100)/";
s = s.substring(s.indexOf("(") + 1, s.indexOf("+"));
Date d = new Date(Long.parseLong(s));
With the same structure, you can find the timezone (+0100) (from "+" to ")") and work with a Calendar to find the right time for the right time area.
First you have to parse out the time value from String i.e. "1411472160000+0100" part.
Here in "1411472160000+0100" , "+0100" is the timezone info. If you don't want to consider the timezone, then you can take following approach.
Approach-1
long timestamp = 1245613885;
Calendar calendar = Calendar.getInstance();
calendar.setTimeZone(TimeZone.getDefault());
calendar.setTimeInMillis(timestamp * 1000);
int year = calendar.get(Calendar.YEAR);
int day = calendar.get(Calendar.DATE);
int hour = calendar.get(Calendar.HOUR_OF_DAY);
int minute = calendar.get(Calendar.MINUTE);
then to get the date in your specified format you can use-
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String dateString = sdf.format(calendar.getTime());
System.out.println(dateString); // 2009-06-21 15:51:25
Besides this approach, there is an excellent Java Date library called JodaTime.
If you want to incorporate the timezone info , you can refer to this constructor from JodaTime.
http://www.joda.org/joda-time/apidocs/org/joda/time/DateTime.html#DateTime-long-org.joda.time.DateTimeZone-
I have the following code in groovy to get current time in hours.
def now = new Date()
def time = now.getHours()
but the getHour() method is deprecated. What are the disadvantages if I use this method and the what is the alternative to this method in groovy/Java ?
Use Calendar,
Calendar cal=Calendar.getInstance();//it return same time as new Date()
def hour = cal.get(Calendar.HOUR_OF_DAY)
For details, read this docs.
Try using Joda Time instead of standard java.util.Date classes. Joda Time library has much better API for handling dates.
DateTime dt = new DateTime(); // current time
int month = dt.getMonth(); // gets the current month
int hours = dt.getHourOfDay(); // gets hour of day
You can use the traditional classes like this to fetch fields from given Date instance.
Date date = new Date(); // given date
Calendar calendar = GregorianCalendar.getInstance(); // creates a new calendar instance
calendar.setTime(date); // assigns calendar to given date
calendar.get(Calendar.HOUR_OF_DAY); // gets hour in 24h format
calendar.get(Calendar.HOUR); // gets hour in 12h format
calendar.get(Calendar.MONTH); // gets month number, NOTE this is zero based!
You can use Joda-time for get current time or getHours
Probably there will be simply and fast answer but I still cant find out why is the result of
Date date = new Date(60000); //one min.
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
String dateStr = dateFormat.format(date);
dateStr - 01:01:00
Still one hour more. Time zone? How can I set it without it? Thanks.
Date represents a specific moment in time, not a duration. new Date(60000) does not create "one minute". See the docs for that constructor:
Initializes this Date instance using the specified millisecond value. The value is the number of milliseconds since Jan. 1, 1970 GMT.
If you want "one minute from now" you'll probably want to use the Calendar class instead, specifically the add method.
Update:
DateUtils has some useful methods that you might find useful. If you want the elapsed time in HH:mm:ss format, you might try DateUtils.formatElapsedTime. Something like:
String dateStr = DateUtils.formatElapsedTime(60);
Note that the 60 is in seconds.
Three ways to use java.util.Date to specify one minute:
1. Using SimpleDateFormat.setTimeZone(TimeZone.getTimeZone("UTC")) as shahtapa said:
Date date = new Date(60*1000); //one min.
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
String dateStr = dateFormat.format(date);
System.out.println("Result = " + dateStr); //Result should be 00:01:00
2. Using java.util.Calendar as kabuko said:
Calendar calendar = Calendar.getInstance();
calendar.clear();
calendar.set(Calendar.MINUTE,1); //one min.
Date date = calendar.getTime();
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
String dateStr = dateFormat.format(date);
System.out.println("Result = " + dateStr); //Result should be 00:01:00
Other calendar.set() statements can also be used:
calendar.set(Calendar.MILLISECOND,60*1000); //one min.
calendar.set(1970,0,1,0,1,0); //one min.
3. Using these setTimeZone and Calendar ideas and forcing Calendar to
UTC Time-Zone
as Simon Nickerson said:
Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
calendar.clear();
calendar.set(Calendar.MINUTE,1); //one min.
Date date = calendar.getTime();
SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss");
dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));
String dateStr = dateFormat.format(date);
System.out.println("Result = " + dateStr); //Result should be 00:01:00
Note: I had a similar issue: Date 1970-01-01 was in my case -3 600 000 milliseconds (1 hour late) java.util.Date(70,0,1).getTime() -> -3600000
I recommend to use TimeUnit
"A TimeUnit represents time durations at a given unit of granularity and provides utility methods to convert across units, and to perform timing and delay operations in these units. A TimeUnit does not maintain time information, but only helps organize and use time representations that may be maintained separately across various contexts. A nanosecond is defined as one thousandth of a microsecond, a microsecond as one thousandth of a millisecond, a millisecond as one thousandth of a second, a minute as sixty seconds, an hour as sixty minutes, and a day as twenty four hours."
http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/TimeUnit.html
Date date = new Date(); // getting actual date
date = new Date (d.getTime() + TimeUnit.MINUTES.toMillis(1)); // adding one minute to the date
I'm a beginner in java/android but I am trying to make an app. A user must type in a time like 13:45 and then the app should substrat ex. 00:30 minutes from that time. That gives the result 13:15.
I have tried many different things but it wont work.
I have somthing like this. (At this stage I've hardcoded two times)
String time1 = "00:30";
String time2 = "13:45";
SimpleDateFormat format = new SimpleDateFormat("HH:mm");
Date date1 = format.parse(time1);
Date date2 = format.parse(time2);
long result= date2.getTime() - date1.getTime();
String strLong = Long.toString(result);
textView4.setText(strLong);
I'm getting an error in the format.parse(time1) and format.parse(time2). Is this the right way to do this? Any help? Thanks
Use Calendar type.
SimpleDateFormat format = new SimpleDateFormat("HH:mm");
Date date2 = format.parse(time2);
Calendar cal=Calendar.getInstance();
cal.setTime(date2);
cal.add(Calendar.MINUTE, -30); //Subtract 30 Min
String strLong= format.format(cal.getTime());
textView4.setText(strLong);