hedate

hedate is a Holocene/Human Era-aware (GNU) date-like utility for converting, formatting, and expressing dates in the Holocene/Human Era calendar system.

What is the Holocene calendar?

https://en.wikipedia.org/wiki/Holocene_calendar

According to Wikipedia: "The Holocene calendar, also known as the Holocene Era or Human Era (HE), is a year numbering system that adds exactly 10,000 years to the currently dominant (AD/BC or CE/BCE) numbering scheme, placing its first year near the beginning of the Holocene geological epoch and the Neolithic Revolution, when humans shifted from a hunter-gatherer lifestyle to agriculture and fixed settlements."

The Holocene/Human Era calendar is a way to date the full span of human history by counting years from the beginning of the Holocene, which marks the start of settled human civilization. It helps simplify mental models of human history.

Date examples:

Event	Human Era Date	Gregorian Date
Start of Holocene Era	0 HE	10 000 BCE
Founding of Athens	9492 HE	508 BCE
Founding of Rome	9247 HE	753 BCE
Conquest of Constantinople	29 May 11453 HE	29 May 1453 CE
Unix Epoch	1 Jan 11970 HE	1 Jan 1970 CE
Present year	12025 HE	2025 CE

Weekdays follow the proleptic Gregorian weekday cycle for all dates, both backward and forward in time.

Usage

hedate --help

Holocene/Human Era date command

Usage: hedate [OPTIONS] [format]...

Arguments:
  [format]...  Format string (prefix with +)

Options:
  -d, --date <STRING>          Date string
      --help                   Print help information
  -u, --utc                    Use Coordinated Universal Time
  -z, --timezone <OFFSET|TZ>   Set timezone offset (e.g., -08:00, +05:30, 08:00) or common abbrev (PST, EST)
      --rfc-2822               Output date and time in RFC 2822 format
      --rfc-email              Output date and time in RFC 5322 format (alias for --rfc-2822)
      --rfc-3339 [<TIMESPEC>]  Output date and time in RFC 3339 format (TIMESPEC: date, seconds, ns) [possible values: date, seconds, ns]
  -I, --iso-8601 [<FMT>]       Output date/time in ISO 8601 format (FMT: date, hours, minutes, seconds, ns) [possible values: date, hours, minutes, seconds, ns]
  -g, --gregorian              Explicitly interpret -d/--date as Gregorian/CE
  -h, --holocene               Explicitly interpret -d/--date as Holocene/Human Era
  -f, --file <DATEFILE>        Read dates to parse from file, one per line
      --debug                  Annotate parsed date and warn about questionable usage
      --resolution             Output available timestamp resolution
  -V, --version                Print version

Format presets:
  --rfc-2822 / --rfc-email   RFC 2822/5322
  --rfc-3339[=date|seconds|ns]
  --iso-8601[=date|hours|minutes|seconds|ns]

Formatting tokens (Holocene-aware replacements):
  %Y/%y/%C   Holocene years (year+10000)
  %E         Era marker: HE
  %s         Seconds since Holocene epoch (-9999-01-01T00:00:00Z)
  %N/%<n>N   Nanoseconds since Holocene epoch (n = digits precision)
  %Z         Timezone abbreviation
Other tokens are passed to chrono/strftime. Relative inputs like "+1 day" are supported.

Weekdays follow the proleptic Gregorian weekday cycle for all dates, both backward and forward in time.

Examples

Current time (local tz)

hedate

Current time UTC

hedate --utc

(alias --universal, -u)

Custom timezone

hedate -z -08:00

Supports offsets like +05:30, 08:00, -06:00, common abbreviations: PST/MST/CST/EST/BST/CET/EET/IST/UTC/GMT, and IANA names such as America/Los_Angeles and Europe/London

Specific date/time

hedate -d "1970/12/31 23:59:59"

Holocene input

hedate -h -d "0337/12/31 12:01:57"

or suffix: -d "0337/12/31 12:01:57 HE"

BCE input

hedate -d "0337/12/31 BCE"

Custom format

hedate "+%m-%d-%Y %H:%M:%S %z %Z %E"

RFC/ISO presets

hedate --rfc-3339

--rfc-2822, --rfc-email, --rfc-3339[=date|seconds|ns], --iso-8601[=date|hours|minutes|seconds|ns]

Relative

hedate -d "+1 day"`, `hedate -d "last week"`, `hedate -d "tomorrow"

File input

hedate -f dates.txt

Resolution

hedate --resolution

Debug parsing

hedate --debug -d "12/31/1970"

Real World Examples

Get the founding of Rome in the Human Era

hedate -d "0753/04/21 BCE" # yyyy/mm/dd
hedate -d "04/21/0753 BCE" # mm/dd/yyyy

Use the Human Era as a timestamp

hedate +%s    # seconds
hedate +%s%3N # miliseconds
hedate +%s%N  # nanoseconds

Behavior

• Calendars: auto-detect -d inputs (Gregorian, BCE/BC, Holocene with HE/human); force with -g/--gregorian or -h/--holocene/--human.
• Timezone: local by default; --utc/--universal/-u for UTC; custom offsets with -z/--timezone/--tz (e.g., -08:00, +05:30, 08:00) plus a few common abbreviations (PST/MST/CST/EST/BST/CET/EET/IST/UTC/GMT).
• Holocene conversion: uses proleptic Gregorian with astronomical year numbering (year 0 exists); Holocene year = astronomical year + 10,000.
• Epoch-based formatters: %s/%N report seconds/nanoseconds since the Holocene epoch (10,000 BCE start), not Unix epoch.
• Era/year replacements: %Y/%y/%C emit Holocene year values; %E emits HE; %Z uses tz abbreviation.
• Other format tokens are passed through to chrono/strftime; padding flags are handled by chrono when not overridden.

Building

cargo build --release

Testing

cargo test