I am working on a Rails app that displays a sports schedule (in a basic table). Each game/event is a db table row. The customer wants all the events to display in chronological order but to also display the time in the event's local timezone.
How can I add a timezone selector to the New action? So that when the customer enters events they can select the event's timezone and input the event's time in that timezone.
Here is what the schedule would look like:
Event 1 7:00 pm EST
Event 2 5:00 pm PST
Event 3 7:00 pm PST
I personally think this is confusing, but it's what they want. Thanks in advance.
Geoff Buesing wrote a great primer on Rails support of time zones back when 2.1 was released.
Okay I am not so sure I understood your question directly but here is my line of thinking there is a library I passed along called tzinfo which is supposed to give Rails the ability to work with timezones so my guess is do the following build a list for a select box (wikipedia has a good complete list) when the user selects the timezone send it to the server which will calculate the appropriate timings now and send back (maybe depending on your architecture you could send only the added hours that should be added or subtracted)
Related
I feel like I'm going round the houses on this one.
In summary, I have a Location model which has opening hours, modelled as opens_at and closes_at in the DB.
All times are stored as UTC in the database.
If I create a location in New York with opens_at set at 08:30 in my form and it gets saved to the DB as 08:30 UTC, why would I need to worry about timezones? I don't want to display the time in local time because the user would then see opening hours of 03:30.
Am I overthinking this? Do I only need to worry about timezones if I have users in multiple countries attending the same event at the same time?
As this is about physical locations, it feels to me that it wouldn't be needed.
If I create a location in New York with opens_at set at 08:30 in my form and it gets saved to the DB as 08:30 UTC, why would I need to worry about timezones?
Because 08:30 in New York is not 08:30 UTC. It's not even the same time for all dates.
It's 13:30 UTC when New York is observing Eastern Standard Time (EST, UTC-5)
It's 12:30 UTC when New York is observing Eastern Daylight Time (EDT, UTC-4)
So, if the location opens at the same time every day, then you must store it in local time. Otherwise you'll be off by an hour one way or the other following the next DST transition.
This can be an issue even for time zones that don't use DST, and even for non-recurring events, because the various governments of the world control the time zones within their borders. They can change whether to start observing DST or stop observing it, the dates and times that DST transitions occur, or their standard offset from UTC. Some give adequate notice when they make such changes, and others do not. There's always some non-zero chance that a given time zone might change its behavior between when you initially recorded the event and when the event takes place. If you recorded using local time, all you need to do is update the time zone data on your systems (which often happens automatically). However, if you recorded the event using UTC then you could be off when converting back after such a change.
In general, future events should always be stored in terms that the event is described - which is almost always in local time of some particular time zone. Store the IANA time zone ID (e.g., "America/New_York") with the location or event so that you can convert when you need to, but converting to UTC prematurely can lead to losing sight of the original information.
Save the "Always UTC" mindset for past or present events, such as timestamping a transaction.
Yes, I actually have run into this. If the user is only going to see the time in the local time zone, then it is not really necessary to save in UTC with time zone. You can save it in local time without time zone.
Reference: Postgres Time without Time Zone
Some developers will say that you should save it in UTC with the time zone, but I can see two arguments against it:
If you don't need it now and you may never need it.
You may not have access to the Time Zone now or may need extra code/complexity to implement and validate.
You can probably add it later if you know the time zone or lat/lon or address.
I'm having a trouble when develop multiple timezones website.
Currently I'm storing time in UTC after some researches and it is working fine in most cases.
But there is one case that I couldn't find solution for it:
There are two kinds of user in two countries which are United States
and Thailand.
User in Thailand is worker (A).
User in US is manager (B).
When A starts working, their activities logged into our system and B
can watch those via a monitoring screen on web app and they can choose
the date on that.
Example user A starts working at 8 AM on 23 June with mobile
app, when B chooses 23 June date on the monitoring screen, they
can see the activities of user on Thailand on 23 June (because the results is queried by UTC time), but the
problem is he should see the activities on 22 June instead of 23
June because the time in Thailand is faster than United States 12
hours.
How can I show to user B activities of user A when he chooses the date 22 June?
You've not asked about any particular technology stack or implementation, so I can only answer from a general perspective.
Concepts worth understanding:
Thailand has a single time zone, which has an offset of UTC+7 all year.
The US has multiple time zones, whose offsets range from UTC-10 to UTC-4, depending on what part of the country you are referring to, whether or not daylight saving time is in effect, and whether or not a particular location observes daylight saving time. (Most of the country does, but all of Hawaii and much of Arizona does not.)
A "date" is just a year, month, and day on a calendar, but the time that which a date is observed is different depending on the time zone of the observer. There is a good visualization of this at everytimezone.com.
In your situation, you will have to decide the behavior you want depending on the specific needs of your application:
Do you want the period shown to represent all activities on the date as observed by the person choosing the date? If so, then determine the start of the current date and the start of the next date in the local time zone of the person selecting the date. Convert those to UTC, and query for all events in that UTC time range.
Example:
Example Activity Time: 2018-06-23T18:00:00+07:00 (Asia/Bangkok)
Stored as UTC: 2018-06-23T11:00:00Z
Date Selected: 2018-06-23 (America/New_York)
Local Range: [2018-06-23T00:00:00-04:00 , 2018-06-24T00:00:00-04:00 )
UTC Range: [2018-06-23T04:00:00Z , 2018-06-24T04:00:00Z )
Query: ... where ActivityUTC >= '2018-06-23 04:00:00' and ActivityUTC < '2018-06-24 04:00:00'
Or, do you want the date selected to always represent the date of the activity in the time zone of the person who recorded that activity, regardless of the time zone of the viewer? If so, then store that local date in a separate date-only column and just query on it without regard to time zone.
Example:
Example Activity Time: 2018-06-23T18:00:00+07:00 (Asia/Bangkok)
Local Date Stored: 2018-06-23
Date Selected: 2018-06-23
Query: ... where ActivityLocalDate = '2018-06-23'
Note, you might still store the UTC date and time in some other field, but it isn't relevant for this particular query.
From prior experience in the time and attendance industry, I can say that if it were me I would want the second option - as workers are typically paid based on their own time zones, not on those of their manager. However their are indeed edge cases and you'll have to decide for yourself which approach best matches your business requirements.
This Answer is specific to MySQL.
If you want B to see what A's clock says, use DATETIME; it will say 8AM.
If you want B to see A logging in in the middle of the night, use TIMESTAMP.
(This extends to A vs B, and to date as well as clock.)
Twice a year, DATETIME has a hiccup between 2AM and 3AM if there is a switch between standard and daylight-savings time.
I am developing a Calendar app where user can select whether he want to auto move the event time based on current timezone or set it as unchanged
based on switch button. I am using Eventkit for storing the events and also UILocalnotification for event notifications
For eg.
Scenario 1:
User set the time of having a walk after dinner as 9pm (IST) everyday in India.He travels to USA but due to timezone change the event notification occurs at 8.30am (PDT) in the morning.What i want is that the event should take place at 9pm (PDT) in USA also.
Scenario 2:
User is in India,He set some online meeting with person in India on Saturday,10pm (IST).He travels to USA,the timezone changed but the meeting should take place at 9.30am (PDT) since its 10pm (IST) in India
The event and notification works in sync,hence need to handle timezone for both ekevent as well as uilocalnotification
Hopefully someone will rescue me from this issue. Thanks
The UILocationNotification allows you to set a fireDate and a timeZone. If you set timeZone to nil, it'll fire at the specified time, adjusting for time zones as you travel (your 2nd case, i.e. a fixed point in time). If you set timeZone to a valid time zone, it'll fire at that time in any time zone (your 1st case, i.e. a variable point in time).
There's a great explanation here
Right, this is a bit confusing for me, so I'm going to try and explain from the top!
I have a rails web app. It's an internal company app and will only be used in the UK.
One of the things the app does is manage meetings.
Meetings have a date & time when they start. There's a date/time picker on the form which allows the user to pick the date & time the meeting is for. I save this date AS IS into the database. All meetings last 2 hours, so the end time is simply start + 2 hours.
Example:
2013-06-23 6:45PM in the form is stored in the db as 2013-06-23 18:45:00
2013-12-23 6.45pm in the form is stored in the db as 2013-12-23 18:45:00
Note that the first date is during Daylight Savings (BST) and the second is during GMT. I don't actually care whether it is GMT or BST: the meeting happens at that time, absolutely.
Inside the rails webapp, I simply print out the exact date & time from the DB - formatted nicely, of course!
Now, at some point I send an email to the organiser of the meeting, and the person they're meeting with. This email tells them the the date & time of the meeting etc, and also includes an iCal (.ics) file for them to put into their (Outlook usually, but also Apple or gmail) calendar.
The issue I am having is that (using the above examples) Outlook shows the meetings like this:
Meeting #1: Start: 23/06/2013 7:45pm, End: 23/06/2013 9:45pm
Meeting #2: Start: 23/12/2013 6:45pm, End: 23/12/2013 8:45pm
Note that it has adjusted the first one because of the BST/GMT thing.
The text of the .ics file contains this code:
Meeting #1:
BEGIN:VCALENDAR
...
DTEND:20130623T204500Z
DTSTART:20130623T184500Z
...
END:VCALENDAR
Meeting #2:
BEGIN:VCALENDAR
...
DTEND:20131223T204500Z
DTSTART:20131223T184500Z
...
END:VCALENDAR
So I am encoding the dates/times using the Z timezone (UTC). I understand this is why Outlook mis converting the UTC time into the BST time for #1 and leaving #2 alone (because GMT == UTC)
My question is: how do I stop this happening? I want the time the meeting is scheduled for to be the absolute, actual time, regardless of GMT/BST: 6:45pm
Should I be storing the date-times as UTC in the DB? How would this be done (I assume it would apply to all dates, not just meeting start dates). And how to re-convert them back into the actual datetime when I display them in the webapp?
Extra:
I have an entry in my initializers/time_formats.rb like this:
:ical => "%Y%m%dT%H%M00Z"
So dates come out like "20130623T184500Z". I use this when building the ics. And this I think is the issue - if the date/time is during BST I don't want to be using Z, but something else?
Your problem is your date/time format. You have:
DTSTART:20130623T184500Z
in your .ics file and this corresponds to 19:45 BST (as British summer time is UTC+1).
There are a few things you should do. First, you can simply remove the 'Z' from the end of your dates. This means that the times inherit the timezone of the calendar, or the underlying application.
This will work assuming that the machines which are running Outlook are all in the Europe/London timezone. If not, or if you want to be a bit safer, you should also specify the following after your BEGIN: VCALENDAR line:
X-WR-TIMEZONE:Europe/London
This specifies the default timezone for all dates which are not specified explicitly.
Finally, if this does not work for any reason then you need to define your datetimes explicitly. First you need to add a timezone definition for Europe/London to the calendar. The info you need is available at http://www.tzurl.org/zoneinfo-outlook/Europe/London.ics. Then you need to ensure that all datetimes are of the format:
DTSTART;TZID=Europe/London:20130623T184500
This last approach is the best, as it means that if your requirements expand to other timezones you will be able to handle them relatively easily.
Sorry to answer this myself, but in case anyone else runs into this here's what I found was the cause of my particular issue. Note that the answer above re timezones also makes sense!
My rails app is storing UTC datetimes in the DB (as is default)
But, it also thought it's own timezone was UTC, which also seems to be the default.
The upshot of that is essentially it was storing local dates, local to UTC anyway. Changing the app to know it was sitting in Europe/London made it so the dates in the DB are all now accurately UTC (meaning, they're an hour off if I'm currently in BST)
I can now use the Z datetime format in iCals, and outlook and the rails app both convert the UTC date back into the actual datetime for the viewing-user's locale (Europe/London for everyone at the moment). This is what I wanted.
Users can create multiple day events.
So an event can have multiple dates, including a start time and end time for the date.
So an event might have these dates:
July 1 2013 9:00am - 5:00pm
July 2 2013 10:00am - 6:00pm
July 7 2013 1:00pm - 5:30pm
So the event table would store the event id, event name, the type of event, address fields for where the event will be held, etc. But how do I model the multiple dates for the event? I could have a separate event_dates table, and that table would have multiple rows for each event:
id event_date event_start_time event_end_time
event1 July 1 2013 9:00am 5:00pm
event1 July 2 2013 10:00am 6:00pm
event1 July 7 2013 1:00pm 5:30pm
But I would also like to query for events occurring on a day (regardless of time), so users could find events in their area that occur on certain days (they might visit multiple events that day).
So how would I model this? Would I use has_and_belongs_to_many, where one event has multiple dates, and one date has multiple events?
In the view, when saving the event, I guess I need to save the event data to the events table, and also save the date/time combination to the other table. But to save the date/time combination to the other table, I need the id for the event that was just saved. So in one form I have a dependency such that the first save must succeed (save event), for the second save to proceed (save date/time using new event id).
Thanks for your help in advance.
I would suggest you set up Event to have many Sessions. Then each session can specify a date/time range for that session.
As far as querying for a particular day goes, you can use a join and a little Rails magic like so: (assuming rails 3.2)
class Event
has_many :sessions
def self.on_day(date)
joins(:sessions).where("session.start < ? AND session.end > ?", date.end_of_day, date.beginning_of_day)
end
have a look at closure_tree gem (https://github.com/mceachen/closure_tree) wich allow you to use acts_as_tree and a hierarchy for your events...
Cheers