Is there an easier way to get start of current day time than this?

I basically want to get zero or beginning hour for currrent day.

def today = Calendar.instance
today.set(Calendar.HOUR_OF_DAY, 0)
tod开发者_StackOverflow中文版ay.set(Calendar.MINUTE, 0)
today.set(Calendar.SECOND, 0)
println today // Mon Mar 15 00:00:00 SGT 2010

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Not simpler than the other solutions, but less lines:

def now = new GregorianCalendar()
def today = new GregorianCalendar(now.get(Calendar.YEAR), now.get(Calendar.MONTH), now.get(Calendar.DAY_OF_MONTH))
println today.getTime()

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You could use the clearTime() function of Calendar in Groovy:

def calendar = Calendar.instance
calendar.with {
  clearTime()
  println time
}

It'd be nice to have a convenience method that clears the time portion of a java.util.Date and/or java.util.Calendar.
There are numerous use cases where it makes sense to compare month/day/year only portions of a calendar or date. Essentially, it would perform the following on Calendar:

void clearTime() {
    clear(Calendar.HOUR_OF_DAY)
    clear(Calendar.HOUR)
    clear(Calendar.MINUTE)
    clear(Calendar.SECOND)
    clear(Calendar.MILLISECOND) 
 }

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Yes, it would be nice to have to have such a method. But if you can settle for a short function then here's mine:

def startOfDay(t) {
    tz = TimeZone.getDefault();
    t +=tz.getOffset(t);
    t -= (t % 86400000);
    t-tz.getOffset(t);
}

print new Date(startOfDay(System.currentTimeMillis()));

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According to Groovy date documentation, it seems that it's the optimal way.

However, using Groovy with keyword, you can compress a little your statements

def today = Calendar.instance
with(today) {
    set Calendar.HOUR_OF_DAY, 0
    set Calendar.MINUTE, 0
    set Calendar.SECOND, 0
}
println today // Mon Mar 15 00:00:00 SGT 2010

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Not quite sure if this is the best way, or indeed correct (not sure if timezone issues will arise from this), but it could work for simple use cases:

Start of day

def today = new Date()
def start = today.clearTime()

End of day

def today = new Date()
def eod

use (TimeCategory) {
    eod = today.clearTime() + 1.day - 1.millisecond
}

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Starting from Java 8 use java.time solution:

LocalDateTime ldt = LocalDateTime.of(LocalDate.now(), LocalTime.MIN);
ldt.toString();