query filter on date portion of datetime creates wrong parameters for mysql CONVERT_TZ function and returns no results

[donaldinho]

I am setting the timezone

tz = timezone.get_fixed_timezone(-300)
timezone.activate(tz)

then I apply the filter. search_date is just a string submitted by the client

matches = query.filter(startDateTime__date=datetime.strptime(search_date, '%Y-%m-%d').date())

the where clause that is produced is

DATE(CONVERT_TZ(`central_soccer_match`.`startDateTime`, 'UTC', '-0500')) = '2017-07-18'

where as it should be

DATE(CONVERT_TZ(`central_soccer_match`.`startDateTime`, 'UTC', '-05:00')) = '2017-07-18'

note the colon in the timezone we are converting to.