Concise Binary Object Representation (CBOR) Tags for Date
RFC 8943
Internet Engineering Task Force (IETF) M. Jones
Request for Comments: 8943 Microsoft
Category: Standards Track A. Nadalin
ISSN: 2070-1721 Independent
J. Richter
pdv Financial Software GmbH
November 2020
Concise Binary Object Representation (CBOR) Tags for Date
Abstract
The Concise Binary Object Representation (CBOR), as specified in RFC
7049, is a data format whose design goals include the possibility of
extremely small code size, fairly small message size, and
extensibility without the need for version negotiation.
In CBOR, one point of extensibility is the definition of CBOR tags.
RFC 7049 defines two tags for time: CBOR tag 0 (date/time string as
per RFC 3339) and tag 1 (POSIX "seconds since the epoch"). Since
then, additional requirements have become known. This specification
defines a CBOR tag for a date text string (as per RFC 3339) for
applications needing a textual date representation within the
Gregorian calendar without a time. It also defines a CBOR tag for
days since the date 1970-01-01 in the Gregorian calendar for
applications needing a numeric date representation without a time.
This specification is the reference document for IANA registration of
the CBOR tags defined.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8943.
Copyright Notice
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Table of Contents
1. Introduction
1.1. Calendar Dates
1.1.1. Example Date Representations
1.2. Comparing Dates
1.3. Comparing Dates and Date/Time Values
2. IANA Considerations
2.1. Concise Binary Object Representation (CBOR) Tags
Registrations
3. Security Considerations
4. References
4.1. Normative References
4.2. Informative References
Acknowledgements
Authors' Addresses
1. Introduction
The Concise Binary Object Representation (CBOR) [RFC7049] provides
for the interchange of structured data without a requirement for a
pre-agreed schema. RFC 7049 defines a basic set of data types, as
well as a tagging mechanism that enables extending the set of data
types supported via an IANA registry.
This specification defines a CBOR tag for a text string representing
a date without a time. The tagged text string is represented as
specified by the RFC 3339 [RFC3339] "full-date" production. Per RFC
3339, this represents a date within the Gregorian calendar.
This specification also defines a CBOR tag for an integer
representing a date without a time. The tagged integer is an
unsigned or negative value indicating the number of days since the
Gregorian calendar date 1970-01-01. As an implementation note, this
value has a constant offset from the Modified Julian Date value
(which is defined by the Smithsonian Astrophysical Observatory as the
number of days since November 17, 1858); this value is the Modified
Julian Date minus 40587.
Note that since both tags are for dates without times, times of day,
time zones, and leap seconds are not applicable to these values.
These tags are both for representations of Gregorian calendar dates.
1.1. Calendar Dates
Calendar dates are used for numerous human use cases, such as marking
the dates of significant events. For instance, John Lennon was born
on October 9, 1940 and died on December 8, 1980. One such use case
is driver's licenses, which typically include a date of birth. The
dates used in this specification use the Gregorian calendar, as do
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