I want to get the current time in milliseconds. I'm using System.currentTimeMillis() but this returns the date as well as the time. I simply want "15:03" in milliseconds, not the date too.
Note that I want an integer and not a formatted string. If it was 08:30, this is the equivalent to 30600 seconds, which is in turn equivalent to 30600000 milliseconds. This is the value I want
Duration.between( todayStart , now ).toMillis() Get the current moment in the wall-clock time used by the people of a certain region (a time zone).
ZoneId z = ZoneId.of( “Africa/Tunis” ) ; ZonedDateTime now = ZonedDateTime.now( z ) ; Get the first moment of the day. Do not assume this is 00:00:00. Let java.time determine.
ZonedDateTime todayStart = now.toLocalDate().atStartOfDay( z ) ; Represent the delta between them, the span of time unattached to the timeline, as a Duration.
Duration d = Duration.between( todayStart , now ) ; A Duration has a resolution of nanoseconds. That is finer than the milliseconds you desire. A convenience method will ignore any microseconds or nanoseconds for you.
long millisSinceStartOfToday = d.toMillis() ; The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.
Where to obtain the java.time classes?
The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.
Use the LocalTime class:
long millis = LocalTime.now().toNanoOfDay() / 1_000_000; Basil Bourque correctly points out that it isn’t always this simple: a Daylight Saving Time change (such as will occur in most of the US this Sunday) can mean that, for example, there may not be eight hours between midnight and 8 AM.
You can account for this by using a ZonedDateTime, which accounts for all calendar information, including DST changeovers:
ZonedDateTime now = ZonedDateTime.now(); ZonedDateTime start = now.truncatedTo(ChronoUnit.DAYS); long millis = ChronoUnit.MILLIS.between(start, now); 
LocalTime of 2 AM when in fact only one hour of milliseconds elapsed.Since you are interested in the millis since midnight in the GMT timezone, the easiest approach is probably:
int millis = LocalTime.now(ZoneOffset.UTC).get(ChronoField.MILLI_OF_DAY); 
.get(ChronoField.MILLI_OF_DAY) very much, it’s so clear to read the intention. Other date-time classes can be used instead of OffsetTime including LocalTime.