Date/time range display

[cogat]

Different sites have different preferences for displaying dates and times. Further, different locales will treat dates and times differently.

The date-range and time-range display functions in eventtools (in utils.pprint_timespan) are pretty unwieldy, and difficult to replace with individual preference. This ticket is to implement an easier structure.

The proposal is to remove pprint_timespan, and define the range formats in a setting, which can be overridden or extended on a per-project basis:

PRETTY_DATE_FORMATS = {
    'DEFAULT': {
        'sep': _(u" to "),
        'date': _(u"%(d1)s %(F1)s %(y1)s"),
        'date_range': _(u"%(d1)s %(F1)s %(y1)s %(sep)s %(d2)s %(F2)s %(y2)s"),
        'date_range_within_year': _(u"%(d1)s %(F1)s %(sep)s %(d2)s %(F2)s %(y2)s"),
        'date_range_within_month': _(u"%(d1)s%(sep)s%(d2)s %(F2)s %(y2)s"),
        'month':  _(u"%(F1)s %(y1)s"),
        'month_range':  _(u"%(F1)s %(y1)s %(sep)s %(F2)s %(y2)s"),
        'today': _(u"today, %(d1)s %(F1)s"),
        'tomorrow': _(u"tomorrow, %(d1)s %(F1)s"),
        'time': _(u"%(h1)s:%(i1)s%(a1)s"),
        'time_range': _(u"%(h1)s:%(i1)s%(a1)s%(sep)s%(h2)s:%(i2)s%(a2)s"),
        'time_range_within_ampm': _(u"%(h1)s:%(i1)s%(sep)s%(h2)s:%(i2)s"),
        'hour': _(u"%(h1)s%(a1)s")
        'hour_range': _(u"%(h1)s%(a1)s%(sep)s%(h2)s%(a2)s")
        'hour_rangewithin_ampm': _(u"%(h1)s%(sep)s%(h2)s%(a2)s")
        'midnight': '12 midnight',
        'noon': '12 noon',
        # I think that is all the special cases.
    },
    'BRIEF': {
        'sep': _(u"–"),
        'date': _(u"%(d1)s/%(m1)s"),
        'date_range': _(u"%(d1)s/%(m1)s%(sep)s%(d2)s/%(F2)s"),
        # etc.
    }
}

Then, in templates, the date can be formatted thus:

{{ events.pretty_date }} to use the DEFAULT format
{{ events.pretty_date_BRIEF }} to use the BRIEF format (using getattr magic).