On Feb 19, 2011, at 6:40 AM, Martijn Moeling wrote:
> Hi,
>
> I would like to store all time values in my database as UTC values
> (automatically). I already have the proper conversion routines in my own
> CALDAV server but I have many more places where I would like to store dates.
>
> what would be a logical place to hook in those conversion routines so that
> DateTime and Time values are stored as UTC in the database automatically. The
> front end code will display the local time as it will consider all values
> from the database as UTC.
The application itself should coerce all dates into UTC as soon as possible.
Its best to assume that "local time" is a moving target only decided at the
very endpoints of the UX, i.e. rendering, data handling. In my experience
this means the date conversions tend to occur in Python. Any date logic or
arithmetic that occurs in Python can proceed normally without any timezone
mismatch. An alternative approach is to use timezone-aware datetimes, but
the effect is similar, as you still need to coerce incoming data into timezone
aware constructs.
So I've got a web application, in my templates I display dates like:
${someobject.created_at | n, formatters.format_datetime_local}
where the function is:
def format_datetime_local(k, format="%Y-%m-%d %H:%M:%S %Z", tz=None):
if k is None:
return ""
if tz is None:
tz = c.tz
k = pytz.utc.localize(k)
k = k.astimezone(tz)
return k.strftime(format)
When I receive user input, I'm using a formencode validator that handles it.
If the scenario is that there's literally no space between your "front end" and
your database routines (which is usually unlikely), TypeDecorator is the
standard construct for data coercion at the point of database interaction -
still an in-python routine.
>
> Martijn
>
>
>
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