On Saturday, May 13, 2017 07:33:35 Russel Winder via Digitalmars-d-learn wrote: > A priori I thought 2015 was a perfectly valid ISO8601 date-time > specification. It appears that SysTime.fromISOString disagrees: > > core.time.TimeException@/usr/include/d/std/datetime.d(8553): Invalid > ISO String: 2015 > > So am I right or wrong. > https://en.wikipedia.org/wiki/ISO_8601https://en.wikipedia.org/wiki/ISO_8 > 601
The ISO representation of a date is YYYYMMDD, and the extended ISO representation is YYYY-MM-DD. YYYY would be a truncated representation. The standard has language such as "If, by agreement, truncated representations are used" to talk about truncated representations, but it's not part of the actual, standard string representation. It's just giving guidance on what applications should do if they decide to not use the full string representation when communicating with one another, and it's not expected that an application that supports the standard would support truncated representations. It's only "by agreement," between two applications, not standard. std.datetime only supports the full, standard string representation, and for SysTime, that also includes the time, not just the date. std.datetime.Date would be the closest, but it represents a date, not just a year, so it's YYYYMMDD or YYYY-MM-DD. If you want to pass a string to SysTime.fromISOString, it's going to need to be YYYYMMDDTHHMMSS (optionally with fractional seconds and a time zone). And really, there isn't much useful that can be done with a SysTime that was constructed from just a year anyway. The best SysTime could do would be to assume you meant 2015-01-01T00:00:00. It operates on the system time in hecto-nanoseconds and really isn't meant be operating on dates (that's what Date and DateTime are for). Converting 2015 to a SysTime with no information would be like trying to construct a time_t in C with just 2015. That usually doesn't make much sense. Nothing in std.datetime operates simply on a year. The closest that you're going to get to that is Date. Regardless, if you know that you're just dealing with a year, and that's it, you can just call to!int on it and pass it to the constructor of SysTime, DateTime, or Date (depending on which you want to use) with whatever values you want to set for the month, day, etc. Using a function like fromISOString would just be overkill if all you have is a year, even if it did accept truncated representations. But the truncated representations are not required by the standard, so they're not supported. - Jonathan M Davis
