Get the UNIX timestamp from UUID version 1

Question

In our Java application we are trying to get the UNIX time from the UUID version 1. But it's not giving the correct date time values.

long time = uuid.timestamp();
time = time / 10000L;   // Dividing by 10^4 as it's in 100 nanoseconds precision 
Calendar c = Calendar.getInstance();
c.setTimeInMillis(time);
c.getTime();

Can someone please help?

Answer 1

From the docs for timestamp():

The resulting timestamp is measured in 100-nanosecond units since midnight, October 15, 1582 UTC.

So you need to offset it from that. For example:

Calendar uuidEpoch = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
uuidEpoch.clear();
uuidEpoch.set(1582, 9, 15, 0, 0, 0); // 9 = October
long epochMillis = uuidEpoch.getTime().getTime();

long time = (uuid.timestamp() / 10000L) + epochMillis;
// Rest of code as before

Answer 2

If you using datastax driver, it's:

UUIDs.unixTimestamp(uuid)

http://www.datastax.com/drivers/java/2.0/com/datastax/driver/core/utils/UUIDs.html#unixTimestamp(java.util.UUID)