In UUIDGenerator, GREG_OFFSET is defined as
// offset to move from 1/1/1970, which is 0-time for Java, to gregorian
// 0-time 10/15/1582, and multiplier to go from 100nsec to msec units
private static final long GREG_OFFSET = 0x01b21dd213814000L;
This constant is used as:
// calculate time as current millis plus offset times 100 ns ticks
long currentTime = (_currentMillis + GREG_OFFSET) * MILLI_MULT;
Based of the usage, GREG_OFFSET should be in msec unit and this value should be
(1970-1582) * 365.25 * 24 * 3600 * 1000 (ms) = 12,219,292,800,000 (ms) = 0xB1D 069B 5400 (ms)
The defined constant value 0x1b21dd213814000L is the last value in 100ns unit not ms.
This also offsets the currentTime calculation off by a factor of 10**4.
To correct the discrepency, either:
1) GREG_OFFSET should assign the value of 0xB1D 069B 5400L instead of 0x1b2 1dd2 1381 4000L, or
2) long currentTime = (_currentMillis * MILLI_MULT ) + GREG_OFFSET ;
Since UUID is an arbituary value, therefore I don't believe the current implementation is "incorrect" but just inconsistent in its implementation description.
Please comment on if:
1) the suggested change will have any undesirable side-effect for UUID
2) there is any legacy/backward compatibility problem
3) this is worth to change at all.
If there is no objection, I'll correct the "problem" early next week.