name: type-date
kind: type
description: Day-granularity date stored as epoch days (signed since 1970-01-01).
type: reference
applies_to: inspect, predict
Bytes
Fixed-width: 4 bytes per record, little-endian. Not bit-packed. Stride contributes 4 bytes to Schema.RecordByteSize. On the wire it is a two’s-complement signed int32; semantically it is days offset from 1970-01-01 (read a raw ReadFieldValue word with encoding.DateDays).
Range
Days since the Unix epoch (1970-01-01). Negative offsets address pre-epoch dates (1969-12-31 is −1, 1900-01-01 is −25567); positive offsets address dates after. Ordering, filters, groupers, min/max, lookup keys and every export adapter honour the sign. The 32-bit width supports a range comfortably wider than any real-world need. Sub-day precision is NOT supported — store sub-day timestamps as u64 microseconds.
Null
Orthogonal. Nullable: true participates in the per-record null bitmap. There is no in-band sentinel — 0 is 1970-01-01, not null. IsNumericForAnalytics() is true, so aggregators treat the ordinal directly with null-skip semantics; IsNumeric() is false (excluded from strict scalar numeric).
Dictionary
Absent. Dates are never dictionary-encoded.
See
- Skill:
cohort-schema-design(Field-type matrix),grouper-design. - Cross-link:
type-u64for sub-day timestamps.