Convert specific datetime to milliseconds in groovy

Question

I am trying to convert specific datetime to millisecond. Then i have to add 15min to the milliseconds. Both the output needs in milliseconds.

TimeZone.setDefault(TimeZone.getTimeZone('UTC'))
d = "21/09/2020"
t = "03:00"
Date unixTimedate = new Date("$d $t:00");
long fromTime = unixTimedate.getTime()
log.info fromTime

def c = new Date(fromTime).format("dd/MM/yyyy'T'HH:mm:ss");
log.info c
d =  new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS").parse(c)
use(TimeCategory)
{
    def startdate2 = d + 15.minutes
    log.info "updated datetime" + startdate2
    def outputDateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS"
    def newstartdatetime = "${startdate2.format(outputDateFormat)}"
    log.info "StartDateTime : " + newstartdatetime
long toTime = newstartdatetime.getTime()
log.info toTime
}

Output: Mon Sep 21 08:17:17 UTC 2020:INFO:1631156400000 which is Thu Sep 09 2021 03:00:00

21 now converted to 09

Answer 1

If you are using JDK 8+ then you can use the Date and Time classes, which are inspired by the fabulous Joda-Time library.

Consider:

import java.time.*
import java.time.format.DateTimeFormatter
import java.util.concurrent.TimeUnit

def formatter = DateTimeFormatter.ofPattern("dd/MM/yyyy'T'HH:mm:ss")
def text1 = "21/09/2020T03:00:00"

def dateTime1 = LocalDateTime.parse(text1, formatter)
def zonedDateTime1 = dateTime1.atZone(ZoneId.of("UTC"))
long milliValue1 = zonedDateTime1.toInstant().toEpochMilli()

def intervalInSeconds = TimeUnit.MINUTES.toSeconds(15)
def milliValue2 = zonedDateTime1.toInstant()
                              .plusSeconds(intervalInSeconds)
                              .toEpochMilli()
def dateTime2 = LocalDateTime.ofInstant(
                    Instant.ofEpochMilli(milliValue2), ZoneId.of("UTC"))
def text2 = dateTime2.format(formatter)

println "milliValue1  : " + milliValue1 
println "text1        : " + text1

println "milliValue2  : " + milliValue2 
println "text2        : " + text2

Output:

milliValue1  : 1600657200000
text1        : 21/09/2020T03:00:00
milliValue2  : 1600658100000
text2        : 21/09/2020T03:15:00