Opened 8 years ago

Closed 8 years ago

#15 closed defect (fixed)

draft-ietf-tzdist-timezone-service-11: truncation of future data

Reported by: eggert@… Owned by: cyrus@…
Priority: major Milestone:
Component: service Version:
Severity: Candidate WG Document Keywords:


Related to: Ticket 11

ection 3.4 talks about truncation as if it applied only to past data, but it also applies to the future. For example, the tz database currently truncates the data for "Asia/Tehran?" after 2037, because Iran's actual rules are based on the Persian calendar and cannot be expressed compactly in tz format (or in VTIMEZONE format, I presume). Worse, some rules are based on astronomical calendars and therefore cannot be predicted into the indefinite future. Because the server cannot represent all the future data, it must truncate. I'm not sure how to fix all this, but here's a draft of a replacement for Section 3.4 that may suggest one way to go:

Timezones and daylight saving times rules have been in use for over a century, and in some timezones it is not practical to represent rules into the indefinite future. Timezone data can thus contain a large amount of historical or predicted information that may not be relevant for a particular server's intended clients. Calendaring and scheduling clients are likely most concerned with timezone data that covers a period near the present, as users typically only create new events for the present and near future. To avoid having to send unnecessary data, servers are allowed to truncate timezone data at some appropriate date in the past or the future or both, and provide accurate offsets and rules only for times within the non-truncated interval. To simplify the set of data a server needs to support, truncation always occurs at the start of a year, i.e., the year's first midnight for the timezone's local time.

When truncating a "VTIMEZONE" component that crosses a truncation boundary, the server MUST adjust it so that appears to be at the start or at the end of the published interval, and its response MUST advertise the truncation dates used.

Change History (2)

comment:1 Changed 8 years ago by lear@…

  • Component set to service
  • Summary changed from draft-douglass-timezone-service-11: truncation of future data to draft-ietf-tzdist-timezone-service-11: truncation of future data

This ticket is addressed with the addition of the TZUNTIL property. Working group participants are invited to review this change to determine if it has properly addressed the issue.

comment:2 Changed 8 years ago by mglt.ietf@…

  • Resolution set to fixed
  • Status changed from new to closed
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