Expand description
Core constants for the BrightDate system.
§Epoch
The BrightDate epoch is J2000.0 — defined by the IAU as
2000-01-01T12:00:00.000 TT (Terrestrial Time). This same instant is:
| Timescale | Wall-clock label |
|---|---|
| TT | 2000-01-01T12:00:00.000 |
| TAI | 2000-01-01T11:59:27.816 |
| UTC | 2000-01-01T11:58:55.816 |
| Julian | JD 2451545.0 |
| Modified | MJD 51544.5 |
BrightDate 0.0 ≡ J2000.0, exactly. Bright days are SI days (86400 SI
seconds), so the BrightDate timeline ticks uniformly (TAI-coherent) and
has no leap-second discontinuities. Leap seconds only intervene when
converting to/from UTC labels (Unix ms, ISO strings).
Constants§
- CURRENT_
TAI_ UTC_ OFFSET - Current TAI − UTC offset (37 s since 2017-01-01; no new leap seconds as of 2026).
- DEFAULT_
PRECISION - Default display precision (5 decimal places ≈ 0.864 s resolution).
- J2000_
JD - J2000.0 as a Julian Date — exact by definition of the J2000.0 epoch.
- J2000_
MJD - J2000.0 as a Modified Julian Date — exact by definition.
- J2000_
TAI_ UNIX_ S - J2000.0 in “TAI Unix seconds” — Unix-style elapsed seconds counted on
the TAI timescale. Equals
946_727_967.816. Used internally as the origin against which BrightDate values are measured. - J2000_
TT_ UNIX_ S - J2000.0 in “TT Unix seconds” (TT label expressed as Unix-style elapsed
seconds on the TT timescale). Equals
946_728_000.000. This is the number the old library wrongly used asJ2000_UNIX_MS_UTC. - J2000_
UNIX_ MS_ UTC Deprecated - Backwards-compatible alias. Deprecated. Use
J2000_UTC_UNIX_MS. - J2000_
UTC_ UNIX_ MS - J2000.0 expressed in Unix milliseconds (a UTC-labelled timestamp).
- LEAP_
SECOND_ TABLE - Leap-second table:
(utc_unix_seconds, cumulative_tai_utc_offset). - LEAP_
SECOND_ TABLE_ REVIEWED_ AT - When the table was last reviewed (ISO date string).
- LEAP_
SECOND_ TABLE_ SOURCE - Source of the leap-second table.
- LEAP_
SECOND_ TABLE_ VALID_ UNTIL_ UNIX_ S - The Unix-seconds timestamp after which the table should be re-checked. 2028-06-28T00:00:00Z
- MAX_
PRECISION - Maximum supported precision (12 decimal places ≈ 86.4 ps).
- METRIC_
UNITS - Metric unit descriptors:
(name, days_per_unit). - MS_
PER_ DAY - Milliseconds per (SI) day.
- SECONDS_
PER_ DAY - Seconds per (SI) day.
- TAI_
UTC_ OFFSET_ AT_ J2000 - TAI − UTC offset at J2000.0 (32 leap seconds had been inserted by then).
- TT_
TAI_ OFFSET_ SECONDS - TT − TAI offset (constant, defined by convention). TT = TAI + 32.184 s.