Java: generate random Date between now minus X months plus Y months

Introduction

This blogpost shows a Java 8+ code example on how to generate a timestamp between two months relative to today ("now").

The code

This example code creates a random java.util.Date between 12 months ago from today until 1 month ahead from today, which will be available in variable randomDate.

LocalDateTime nowMinusYear = LocalDateTime.now().minusMonths(12);

ZonedDateTime nowMinusYearZdt = nowMinusYear.atZone(ZoneId.of("Europe/Paris"));

beginTimeInMilliseconds = nowMinusYearZdt.toInstant().toEpochMilli();

LocalDateTime nowPlusMonth = LocalDateTime.now().plusMonths(1);

ZonedDateTime nowPlusMonthZdt = nowPlusMonth.atZone(ZoneId.of("Europe/Paris"));

endTimeInMilliseconds = nowPlusMonthZdt.toInstant().toEpochMilli();

System.out.println("System.out.currentInmillis = " + System.currentTimeMillis() + ", beginTimeInMilliseconds = " + beginTimeInMilliseconds + ", endTimeInMilliseconds = " + endTimeInMilliseconds);

Date randomDate = new Date(getRandomTimeInMillisBetweenTwoDates());
...

private static long getRandomTimeInMillisBetweenTwoDates() {

   long diff = endTimeInMilliseconds - beginTimeInMilliseconds + 1;

   return beginTimeInMilliseconds + (long) (Math.random() * diff);

}

Reference: https://stackoverflow.com/questions/23944370/how-to-get-milliseconds-from-localdatetime-in-java-8