How can I find the amount of seconds passed from t

问题:

I need a function that gives me how many seconds passed from the midnight. I am currently using System.currentTimeMillis() but it gives me the UNIX like timestamp.

It would be a bonus for me if I could get the milliseconds too.

回答1:

If you're using Java >= 8, this is easily done :

ZonedDateTime now = ZonedDateTime.now();
ZonedDateTime midnight = now.atStartOfDay()
Duration duration = Duration.between(midnight, now);
long secondsPassed = duration.getSeconds();

If you're using Java 7 or less, you have to get the date from midnight via Calendar, and then substract.

Calendar c = Calendar.getInstance();
long now = c.getTimeInMillis();
c.set(Calendar.HOUR_OF_DAY, 0);
c.set(Calendar.MINUTE, 0);
c.set(Calendar.SECOND, 0);
c.set(Calendar.MILLISECOND, 0);
long passed = now - c.getTimeInMillis();
long secondsPassed = passed / 1000;

回答2:

java.time

Using the java.time framework built into Java 8 and later. See Tutorial.

import java.time.LocalTime
import java.time.ZoneId

LocalTime now = LocalTime.now(ZoneId.systemDefault()) // LocalTime = 14:42:43.062
now.toSecondOfDay() // Int = 52963

It is good practice to explicit specify ZoneId, even if you want default one.

回答3:

tl;dr

Duration.between( todayStart , now )
        .getSeconds()

java.time

Java 8 and later has the java.time framework baked in.

By using ZonedDateTime and time zone, we are handling anomalies such as Daylight Saving Time (DST). For example, in the United States a day can be 23, 24, or 25 hours long. So the time until tomorrow can vary by ±1 hour from one day to another.

First get the current moment.

ZoneId z = ZoneId.of( "America/Montreal" );
ZonedDateTime now = ZonedDateTime.now( z );

Now extract the date-only portion, a LocalDate, and use that date to ask java.time when that day began for our desired time zone. Do not assume the day began at 00:00:00. Anomalies such as Daylight Saving Time (DST) mean that the day may begin at another time such as 01:00:00.

ZonedDateTime todayStart = now.toLocalDate().atStartOfDay( z );  // Crucial to specify our desired time zone!

Now we can get the delta between the current moment and the start of today. Such a span of time unattached to the timeline is represented by the Duration class.

Duration duration = Duration.between( todayStart , now );

Ask the Duration object for the total number of seconds in the entire span of time.

long secondsSoFarToday = duration.getSeconds();

---

About java.time

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.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and Java SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP….

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.

回答4:

The simplest and fastest method to get the seconds since midnight for the current timezone:

One-time setup:

static final long utcOffset = TimeZone.getDefault().getOffset(System.currentTimeMillis());

If you use Apache Commons, you can use DateUtils.DAY_IN_MILLIS, otherwise define:

static final long DAY_IN_MILLIS = 24 * 60 * 60 * 1000;

And then, whenever you need the time...:

int seconds = (int)((System.currentTimeMillis() + utcOffset) % DateUtils.DAY_IN_MILLIS / 1000);

Note that you'll need to re-setup if there's a possibility that your program will run long enough, and Daylight Saving Times change occurs...

回答5:

Use getTime().getTime() instead of getTimeInMillis() if you get an error about calendar being protected. Remember your imports:

import java.util.*; 

will include them all while you are debugging:

    Calendar now = Calendar.getInstance();
    Calendar midnight = Calendar.getInstance();
    midnight.set(Calendar.HOUR_OF_DAY, 0);
    midnight.set(Calendar.MINUTE, 0);
    midnight.set(Calendar.SECOND, 0);
    midnight.set(Calendar.MILLISECOND, 0);
    long ms = now.getTime().getTime() - midnight.getTime().getTime();
    totalMinutesSinceMidnight = (int) (ms / 1000 / 60);

回答6:

(System.currentTimeMillis()/1000) % (24 * 60 * 60)

回答7:

Using JodaTime you can call:

int seconds = DateTime.now().secondOfDay().get();
int millis = DateTime.now().millisOfDay().get();

回答8:

Like @secmask, if you need milli-seconds since GMT midnight, try

long millisSinceGMTMidnight = System.currentTimeMillis() % (24*60*60*1000);