| Internet-Draft | IMDF | August 2026 |
| Henlich | Expires 25 February 2027 | [Page] |
This document defines the Internet Month-Name Date Format (IMDF), a concise date representation for English-language human communication.¶
IMDF requires an alphabetic month abbreviation. This makes the month visually distinct from the numeric day and reduces errors caused by differing regional date-order conventions.¶
The specification primarily defines how IMDF dates are presented. It establishes a preferred output form and permits a limited set of familiar English-language variants. Detailed input handling is outside its scope.¶
IMDF does not replace ISO 8601 for machine interchange, language- neutral communication, chronological sorting, or timestamps.¶
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶
This Internet-Draft will expire on 25 February 2027.¶
Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
All-numeric date formats can be misinterpreted when readers use different regional conventions. For example:¶
Such forms do not visually identify which numeric field is the day and which is the month. A reader may automatically apply a familiar ordering and fail to notice that the writer intended another one.¶
Several established protocol specifications demonstrate the long-standing Internet practice of using alphabetic month abbreviations to eliminate date ambiguity. These include ARPA Internet text messages (RFC 822 [RFC0822]), Internet Message Format (RFC 5322 [RFC5322]), and HTTP Semantics (RFC 9110 [RFC9110]). However, those formats include protocol-heavy elements (timestamps, mandatory seconds, or time-zone offsets) optimized for machine parsing rather than concise human communication.¶
IMDF addresses this problem by extracting that proven principle, using an English alphabetic month abbreviation, and applying it to a streamlined, presentation-only format for human-facing text:¶
In each example, the alphabetic component unmistakably identifies the month. The primary objective of IMDF is to reduce human interpretation errors in English-language date communication.¶
IMDF is guided by the following principles.¶
A month should never be mistaken for a day.
Every IMDF date contains an alphabetic month abbreviation. The
month is therefore visually distinct from the numeric day.¶
Favor brevity.
IMDF uses three-letter month and weekday abbreviations so that
dates remain practical in messages, comments, tickets, reports,
presentations, and calendar annotations.¶
Avoid number following number.
Alternating numeric and alphabetic components makes the date
structure easier to recognize. IMDF favors 05 Jan 2026
rather than an all-numeric sequence such as 05 01 2026.¶
Respect established English-language conventions.
IMDF permits limited day-month and month-day variation when no
year is shown. This accommodates familiar English-language
usage without making the month ambiguous.¶
Prefer a unique canonical representation.
IMDF defines one preferred output form for consistent
presentation.¶
IMDF represents a calendar date for human-readable English-language output.¶
An IMDF date MAY include a year or MAY omit it. When omitted, the year may be understood from context, supplied by surrounding text or metadata, intentionally irrelevant, or omitted because the date is recurring. IMDF does not define how an omitted year is interpreted.¶
IMDF does not represent an instant, time of day, duration, or time zone.¶
ISO 8601 [ISO8601] SHOULD be used when language neutrality, machine interchange, chronological sorting, or non-English interoperability is required.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
A "producer" is a person or implementation that presents an IMDF date. "Canonical form" means the preferred output representation defined in Section 3.¶
Producers SHOULD present IMDF dates in this canonical form:¶
[ddd, ]DD MMM[ YYYY]¶
where:¶
ddd is an optional weekday abbreviation;¶
DD is a two-digit day of the month;¶
MMM is a three-letter month abbreviation; and¶
YYYY is an optional four-digit year.¶
Canonical examples:¶
The month MUST be represented by one of these English abbreviations:¶
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec¶
The first letter SHOULD be uppercase and the remaining letters lowercase.¶
In canonical output, the day MUST contain two decimal digits. A leading zero MUST be used for days 1 through 9.¶
Examples:¶
When present, the year MUST contain four decimal digits and MUST follow the month.¶
Examples:¶
Month-day-year output is not IMDF:¶
Jan 05 2026¶
A weekday MAY be included using one of these English abbreviations:¶
Mon Tue Wed Thu Fri Sat Sun¶
In canonical output, the weekday MUST precede the day and MUST be followed by a comma and one space.¶
Examples:¶
The weekday SHOULD correspond to the represented calendar date when the year is known.¶
The syntax of IMDF dates is specified using Augmented Backus-Naur Form (ABNF) as defined in [RFC5234].¶
imdf-date = imdf-canonical / imdf-yearless
; Canonical Form
imdf-canonical = [ weekday ", " ] day " " month [ " " year ]
; Permitted Yearless Variants
imdf-yearless = imdf-day-first-var / imdf-month-first-var
imdf-day-first-var = [ weekday [ "," ] " " ] day-opt-zero " " month
imdf-month-first-var = [ weekday ", " ] month " " day-opt-zero
; Core Elements
day = 2DIGIT ; 01-31
day-opt-zero = 1*2DIGIT ; 1-31 or 01-31
month = "Jan" / "Feb" / "Mar" / "Apr"
/ "May" / "Jun" / "Jul" / "Aug"
/ "Sep" / "Oct" / "Nov" / "Dec"
weekday = "Mon" / "Tue" / "Wed" / "Thu"
/ "Fri" / "Sat" / "Sun"
year = 4DIGIT ; 0000-9999
¶
A limited set of noncanonical variants MAY be used when the year is absent. These variants reflect common English-language usage while retaining an alphabetic month.¶
Producers SHOULD use the canonical form unless a permitted variant is more natural in the surrounding text.¶
In a yearless day-month date, the comma after a weekday MAY be omitted:¶
Mon 05 Jan¶
The canonical equivalent is:¶
Mon, 05 Jan¶
Canonical output:¶
[ddd, ]DD MMM[ YYYY]¶
Additional permitted yearless output:¶
[ddd ]D[D] MMM [ddd, ]MMM D[D]¶
The following rules summarize IMDF output:¶
The month is always alphabetic.¶
A displayed year always follows the month.¶
Canonical output always places the day before the month.¶
Canonical output always uses a two-digit day.¶
Canonical output uses a comma after a displayed weekday.¶
Month-day order is permitted only when the year is absent.¶
A weekday before a month-day date always requires a comma.¶
IMDF is intended for English-language human-facing content such as:¶
ISO 8601 SHOULD be preferred for:¶
multilingual or language-neutral communication;¶
machine interchange and software interfaces;¶
database storage;¶
chronological filename sorting; and¶
applications requiring a standardized numeric date.¶
A date-time format containing an offset or other time-zone information MUST be used when an absolute instant is required.¶
IMDF uses English ASCII weekday and month abbreviations. Localized names are not IMDF.¶
IMDF SHOULD be used only where English-language date notation is expected and understood. A localized format or ISO 8601 SHOULD be used in other language contexts.¶
Ambiguous date interpretation can cause incorrect scheduling, retention, validity, or processing decisions. IMDF reduces this risk by making the month alphabetic and visually distinct from the numeric day.¶
A yearless IMDF date does not identify a unique calendar year. A specific year MUST NOT be assumed unless it is provided by context outside IMDF.¶
IMDF contains neither a time of day nor a time zone. It MUST NOT be used to represent an absolute instant.¶
This document has no IANA actions.¶
24 August 2026 - Full month names are not defined.¶
24-AUG-2026 - Hyphens are not defined.¶
2026 Aug 24 - Year-first order is not defined.¶
Jan 05 2026 - Month-day order cannot include a year.¶
Mon 24 Aug 2026 - A weekday before a dated year needs comma.¶
Mon Jan 05 - Month-day order requires a weekday comma.¶
24/08/2026 - The month is numeric.¶
2026-08-24 - This is ISO 8601, not IMDF.¶