Eleventy ISO8601 Date Parser

Features:

• Zero dependency super minimal ISO8601 date parsing library. Alternatives were too lax, inaccurate, huge on disk, or huge in bundle.
• All dates supported by this library are RFC-9557 compatible (parseable by Temporal.PlainDate.from, Temporal.Instant.from, or Temporal.PlainDateTime.from) to prepare for wider Temporal API support.
  • Note that this is not a full polyfill — not all RFC-9557 dates are supported here. Alternatives: temporal-polyfill or js-temporal/temporal-polyfill
• Invalid strings throw errors.
• Time zone notes:
  • Defaults to UTC when time zone is unknown (not local time). This matches previous behavior in Eleventy and this feature maintains consistency between build and deploy servers.
  • Supports +00, +00:00, -00, or -00:00 style time zone offsets (: delimiter is optional)
• Delimiter notes:
  • Requires the T delimiter with DateTime strings
  • Delimiters in dates (-) and times (:) are optional

Not supported (for RFC 9557 compatibility):

• Standalone time formats are not supported (must be Date or DateTime)
• ISO week date syntax is not supported (e.g. YYYY-W01-1)
• Day of year syntax is not supported (e.g. YYYY-001, YYYY-365)
• Fractional hours or minutes (e.g. T14.6 or T10:30.6) are not supported. Fractional seconds (e.g. milliseconds) are supported (of course).

Usage

npm install @11ty/parse-date-strings

import { parse } from "@11ty/parse-date-strings

// `parse` returns JavaScript Date

parse("2000-01-01") instanceof Date
// true

parse("2000-01-01").toUTCString()
// "Mon, 01 Jan 2001 00:00:00 GMT"

Comparisons

luxon

More strict parsing compared with Luxon’s fromISO (used in Eleventy v0.x through v3):

2016-05-25
20160525
2016-05-25T09
2016-05-25T09:24
2016-05-25T09:24:15
2016-05-25T09:24:15.123
2016-05-25T0924
2016-05-25T092415
2016-05-25T092415.123
2016-05-25T09:24:15,123

# No YYYY or YYYYMM syntax
2016                      # Dropped
2016-05                   # Dropped
201605                    # Dropped

# No ISO week date syntax
2016-W21-3                # Dropped
2016W213                  # Dropped
2016-W21-3T09:24:15.123   # Dropped
2016W213T09:24:15.123     # Dropped

# No day of year syntax (e.g. 200th day of the year)
2016-200                  # Dropped
2016200                   # Dropped
2016-200T09:24:15.123     # Dropped

# No implied current day (time-only syntax)
09:24                     # Dropped
09:24:15                  # Dropped
09:24:15.123              # Dropped
09:24:15,123              # Dropped