How to query records in multiple time zones using their own time zones with Rails or raw SQL

Question

Here's my issue: I have records stored in my DB with UTC time zones but! I need to query those records and return everything within a day according the record's own time zone, regardless of its UTC date.

Example?

Let's say I have a record uploaded at 00:30 on a Tuesday in America/Denver and I have a bunch of records uploaded at 00:30 on a Monday in America/Los_Angeles .

Alright, now, when I query for records made on Monday, the whole day, I'm getting that Tuesday record because 00:30 in America/Denver is technically on Monday in America/Los_Angeles . I'm running raw SQL to try and solve this in my Rails project, but... no dice.

Any help on this?

SELECT
DATE(uploaded_at AT TIME ZONE 'UTC' AT TIME ZONE areas.iso_time_zone) as uploaded_at,
count(DISTINCT photos.id)
FROM photos, areas
WHERE photos.category IN ('landscape', 'family', 'animal', 'saucy', 'feet', 'portrait')
AND photos.uploaded_at
BETWEEN '2017-03-27 00:00:00 UTC' AND '2017-04-02 23:59:59 UTC'
GROUP BY DATE(uploaded_at AT TIME ZONE 'UTC' AT TIME ZONE areas.iso_time_zone)
ORDER BY DATE(uploaded_at AT TIME ZONE 'UTC' AT TIME ZONE areas.iso_time_zone);

Answer 1

Use the in_time_zone method. Docs here: http://apidock.com/rails/DateTime/in_time_zone

Ex. usage:

t = foo.start_time
=> 2000-01-01 14:20:00 UTC
t.zone
=> "UTC"
t.in_time_zone("America/New_York")
=> Sat, 01 Jan 2000 09:20:00 EST -05:00

You can use this to convert the times based on their corresponding timezone thus giving you the proper range to query the UTC records.

Answer 2

Here I am adding on top of @bkunzi01's answer:

There is no way to find out a record's timezone now. So in your action you'll have to provide a timezone based on user's timezone or some logic.

Then use the in_time_zone method. Docs here: http://apidock.com/rails/DateTime/in_time_zone

Ex. usage:

t = foo.start_time
=> 2000-01-01 14:20:00 UTC
t.zone
=> "UTC"
t = t.in_time_zone("America/New_York").at_end_of_day
=> Sat, 01 Jan 2000 09:20:00 EST -05:00
Model.where("created_at > ?", t - 24.hours)

You can use this to convert the times based on their corresponding time zone thus giving you the proper range to query the UTC records.

Answer 3

Something you can do in your WHERE clause. Hope it helps.

BETWEEN IIF(TimeZone=-4,substract 4 hours to UTC time,
IIF(TimeZone=-5,substract 5 hours to UTC time,
IIF(TimeZone=-6,substract 6 hours to UTC time,
IIF(TimeZone=-7,substract 7 hours to UTC time,
IIF(TimeZone=-8,substract 8 hours to UTC time, UTC Time))))) 
AND 
IIF(TimeZone=-4,substract 4 hours to UTC time,
IIF(TimeZone=-5,substract 5 hours to UTC time,
IIF(TimeZone=-6,substract 6 hours to UTC time,
IIF(TimeZone=-7,substract 7 hours to UTC time,
IIF(TimeZone=-8,substract 8 hours to UTC time, UTC Time)))))