Here are some comments on the time-zone-related parts of your Internet Draft ``MIME Calendaring and Scheduling Content Type'' <URL:ftp://ds.internic.net/internet-drafts/draft-ietf-calsch-csct-00.txt> (November 1996). Please let me know if you have any questions about these comments, and I'd appreciate hearing about any updates to your draft. The comments below are similar to comments I've made about draft-ietf-calsch-sch-00.txt and draft-newman-datetime-00.txt, which I can forward if you're interested. 3.1.3.7 Date and Time The examples do not match the grammar in the use of the character `T' to separate date and time. The grammar specifies date followed by time; the examples use `T'. The grammar is to be preferred here. Common practice (allowed by ISO 8601) is to write the date followed by a space followed by time; this is easier for humans to read. ISO 8601 allows fractions to be preceded by `.' instead of `,'; this should be allowed by the grammar. The grammar allows a utc-offset without a sign; this should be fixed, as utc-offsets always have a sign in ISO 8601. Also, common practice (allowed by ISO 8601) is to omit the `:' and minutes of a UTC offset when minutes are zero. Here is a proposed patch: utc-offset = (_+_ / _-_) hour [[_:_] minute] Following the above suggestions, the examples can be expressed as follows in the extended notation: 1996-04-15 08:30:00-05 1996-04-15 13:30:00Z 3.1.5.2 Daylight Savings Rule 3.1.5.5 Time Zone The underlying model in these sections is too simplistic. It assumes that there is a ``standard time zone'' for the home calendar system, together with a single date and time for entering and exiting daylight saving time. However, locations sometimes alter the UTC offset of standard time (e.g. Portugal and Sri Lanka in 1996). Also, some locales have observed double daylight saving time for part of the summer (e.g. Britain in 1947), and two transitions do not suffice to represent this. The model should be fixed to allow an arbitrary sequence of UTC offset changes. If necessary, each change could be labeled by a daylight saving flag (to say whether the resulting time is considered to be ``daylight saving''), and a string label (e.g. `EST') that can be internationalized (e.g. to `HNE' for French-speakers in Montreal). I suggest that you consult the public domain time zone database maintained by Olson et al (<URL:ftp://elsie.nci.nih.gov/pub/>, updated regularly) for ideas about how time zone and daylight saving information could be represented. For example, you could pass labels that identify time zone and daylight saving rules. In the Olson scheme, the label `America/Los_Angeles' identifies the complete UTC offset history for Los Angeles from to the introduction of standard time in 1883 to the indefinite future. The Olson database is updated as governments change the rules, so the label `America/Los_Angeles' can be used by application programs without worrying about the details. By the way, the proper term is ``daylight saving time'', not ``daylight savings time'' (at least, that is what the OED and the Random House Unabridged Dictionary prefer).