Erratum — draft-fossil-artifact-format-01 §4.6.4

Document	draft-fossil-artifact-format-01
Section	4.6.4 — Timestamps (form 5, the bare Julian day number)
Type	Technical (the lexical form and the out-of-range outcome are unstated)
Status	Applied in draft-fossil-artifact-format-01 (2026-10-12)
Reported	2026-10-12
Submitter	Dan Mestas
Found via	A reader implementing §4.6.4 from the text alone

1. Summary

Form 5 says a timestamp token may be "a bare decimal number, treated as a Julian day number when its value r satisfies 0 < r < 5373484.5". It does not say what spellings count as a bare decimal number, and it gives no outcome for a number outside that range: "treated as ... when" states a condition without saying what happens when the condition fails.

2. Location

§4.6.4, item 5, and the "Finally:" paragraph after the field-constraint paragraph.

3. The reference behavior

Verified against Fossil 2.28 by reading src/manifest.c and the bundled SQLite.

The D and E card tokens are handed unchanged to the storage engine's julianday() function (manifest.c:644, :660), and the card is rejected when the result is not positive. That function recognizes a numeric token by its text-to-float conversion (sqlite3AtoF, parseDateOrTime): an optional sign, digits with an optional fraction, and an optional decimal exponent, in the forms [+-]digits[E[+-]digits], [+-]digits.[digits][E[+-]digits] and [+-].digits[E[+-]digits]. Hexadecimal, infinity and NaN spellings are not numbers. The value is converted to whole milliseconds, (i64)(r*86400000 + 0.5) (setRawDateNumber), and kept only when that lies in 0 .. 464269060799999 (validJulianDay); otherwise the function yields no value and Fossil rejects the card. A value that rounds to 0 milliseconds passes the engine's check but fails Fossil's positivity test. The accepted range is therefore 0 < r < 5373484.5 measured after rounding to the millisecond: a positive value below about 5.8e-9 is rejected, and so is a value within about 6e-9 below 5373484.5.

4. Impact

Observable. Two readers can disagree on whether 2.45e6, +2451545.5 or .5 is a valid D card, and on whether 5373484.5 is rejected or read some other way. Fossil accepts the first three and rejects the fourth.

5. Correction

 5.  A bare decimal number, treated as a Julian day number when its
-    value r satisfies 0 < r < 5373484.5.
+    value r satisfies 0 < r < 5373484.5.  The number is an optional
+    sign, then digits with an optional fraction (at least one digit
+    in all), then an optional decimal exponent introduced by E or e
+    with an optional sign, such as 2451545.5, +2451545, .5 or 2.45e6.
+    No other numeric spelling is recognized.  A number whose value
+    is zero, negative, or 5373484.5 or more MUST be rejected.  The
+    check is made on the value rounded to the nearest millisecond,
+    so a positive value that rounds to zero is rejected, as is a
+    value just below 5373484.5 that rounds up to it.

6. Rationale

The grammar is the engine's own, stated so a reader need not consult it. The rejection outcome is what Fossil does; without it the text leaves the over-limit case open.

7. Verification

• Source: Fossil 2.28 src/manifest.c:642-646 and :656-662; bundled SQLite parseDateOrTime, setRawDateNumber, validJulianDay, and the sqlite3AtoF contract.