This document registers tags for serializing date, time of day and a time zone designator in Concise Binary Object Representation (CBOR) (ref. 1).
Many areas of daily life require date and time information. For example, birthdays or opening hours. CBOR tag 1 provides only a coding for time points. A major disadvantage is that a specific date or time can only be interpreted in conjunction with a time zone or a UTC offset. This document proposes two new tags so that the date and time can be encoded individually.
A date consists of three components: year, month and day.
A time consists of 2 to 4 components. Hour, minute, optional second, optional fractional second.
In addition, a tag is specified for the coding of a IANA time zone designator.
Some programming languages have built-in support for date, time or time zone objects. C++ has a proposal to add support to its standard library. (As of 2019)
A date in CBOR has tag 100 and is encoded as a positive or negative integer or a text string. The integer counts the days since 1970-01-01. The text string encodes the date in ISO 8601 format "YYYY-MM-DD".
A time of day in CBOR has tag 116 and is encoded as a positive integer or a floating point number or a text string. The integer and floating point number encode the (fractional) seconds since midnight. The text string encodes the time in ISO 8601 format "hh:mm", "hh:mm:ss" or "hh:mm:ss.sss". The last one contains fractional seconds "sss". Fractional seconds have at least 1 decimal place and are not limited to any length.
A time zone has the tag 122 and is encoded as a text string.
A CBOR decoder can treat data items with tag 100, 116 or 122 that don't meet the criteria above as an error, but this specification doesn't define how a CBOR implementation ought to behave in this case. Section 3.4 of RFC 7049 (ref. 1) details this kind of error-handling behavior.
The following example shows how the date 2018-12-31 is encoded.
D8 64 # tag(100)
19 45E8 # unsigned(17896)
The following example shows how the time 12:00:05 is encoded.
D8 74 # tag(116)
19 A8C5 # unsigned(43205)
The following example shows how the time zone "America/New_York" is encoded.
D8 7A # tag(122)
70 # text(16)
416D65726963612F4E65775F596F726B # "America/New_York"
Ref. 1. Bormann, C. and Hoffman, P. "Concise Binary Object Representation (CBOR)". RFC 7049, October 2013.
Jörg Richter (joerg.richter at pdv-fs dot de)
Any copyright to this specification is released to the Public Domain. http://creativecommons.org/publicdomain/zero/1.0/