The javadoc for UUID says the following about the timestamp field:
The 60 bit timestamp value is constructed from the time_low, time_mid, and time_hi fields of this UUID. The resulting timestamp is measured in 100-nanosecond units since midnight, October 15, 1582 UTC.
(emphasis mine)
The Java timestamp is in milliseconds since 1970-01-01. In order to get a meaningful date from a UUID, you'll need to do two things: convert from 100ns to 1ms precision (divide by 10000) and rebase from 1582-10-15 to 1970-01-01, which you can do by adding a constant value.
WolframAlpha tells us that 1582-10-15 corresponds to a UNIX timestamp of -12219292800, so to get the correct date, you must add 12219292800 to the number of milliseconds you got after dividing by 10000.
As a side note:
The timestamp value is only meaningful in a time-based UUID, which has version type 1. If this UUID is not a time-based UUID then this method throws UnsupportedOperationException.
...so make sure your code either only ever encounters Type 1 UUID's, or can handle that they don't have a timestamp.
