Welcome

• Yes, I'm using the latest release.
• Yes, I've searched similar issues on GitHub and didn't find any.

What did you expect to see?

The maximum UUIDv7 should have a timestamp that evaluates to the year 10889 per https://www.rfc-editor.org/rfc/rfc9562.html#section-6.1-2.8

Length:
The length of a given timestamp directly impacts how many timestamp ticks can be contained in a UUID before the maximum value for the timestamp field is reached. Take care to ensure that the proper length is selected for a given timestamp. UUIDv1 and UUIDv6 utilize a 60-bit timestamp valid until 5623 AD; UUIDv7 features a 48-bit timestamp valid until the year 10889 AD.

What did you see instead?

The maximum UUIDv7 had a timestamp that evaluated to the year 2121.

go test -v -timeout 30s -run ^TestTimestampFromV7$ github.com/gofrs/uuid/v5 -race -count=1 -v

=== RUN   TestTimestampFromV7
    uuid_test.go:275: 1969-12-31 18:00:00 -0600 CST <nil>
    uuid_test.go:275: 2023-09-13 14:02:18.605 -0500 CDT <nil>
    uuid_test.go:275: 2121-04-11 06:53:25.0117257 -0500 CDT <nil>
--- PASS: TestTimestampFromV7 (0.00s)
PASS
ok  	github.com/gofrs/uuid/v5	1.194s

This is likely because of inappropriate function re-use between v1 and v7 and an overflow somewhere (though I haven't fully debugged to prove that):

uuid.go:84-67

// Timestamp is the count of 100-nanosecond intervals since 00:00:00.00,
// 15 October 1582 within a V1 UUID. This type has no meaning for other
// UUID versions since they don't have an embedded timestamp.
type Timestamp uint64

const _100nsPerSecond = 10000000

// Time returns the UTC time.Time representation of a Timestamp
func (t Timestamp) Time() (time.Time, error) {
	secs := uint64(t) / _100nsPerSecond
	nsecs := 100 * (uint64(t) % _100nsPerSecond)

	return time.Unix(int64(secs)-(epochStart/_100nsPerSecond), int64(nsecs)), nil
}

Reproduction steps

Simple patch to the existing test file to see the values embedded in already-present tests:


diff --git a/uuid_test.go b/uuid_test.go
index 6dc97f9..7837c45 100644
--- a/uuid_test.go
+++ b/uuid_test.go
@@ -271,6 +271,10 @@ func TestTimestampFromV7(t *testing.T) {
        for _, tt := range tests {
                got, err := TimestampFromV7(tt.u)
 
+               if err == nil {
+                       t.Log(got.Time())
+               }
+
                switch {
                case tt.wanterr && err == nil:
                        t.Errorf("TimestampFromV7(%v) want error, got %v", tt.u, got)




go test -v -timeout 30s -run ^TestTimestampFromV7$ github.com/gofrs/uuid/v5 -race -count=1 -v

=== RUN   TestTimestampFromV7
    uuid_test.go:275: 1969-12-31 18:00:00 -0600 CST <nil>
    uuid_test.go:275: 2023-09-13 14:02:18.605 -0500 CDT <nil>
    uuid_test.go:275: 2121-04-11 06:53:25.0117257 -0500 CDT <nil>
--- PASS: TestTimestampFromV7 (0.00s)
PASS
ok  	github.com/gofrs/uuid/v5	1.194s

Version of flock

N/A

Logs

N/A

Go environment

go version go1.23.3 darwin/arm64

Validation

• Yes, I've included all information above (version, config, etc.).