I have an icalendar I generate via PHP so people can download the latest schedule to their phones. It works great except that the game times are off by 6 hours on my iPhone. The game time is perfectly fine displaying on Windows calendar.
I've tried playing with the timezones and times but cannot get them to be equal on all platforms.
The calendar is viewable at:
webcal://cal.outbackthunder.com
Dawson,
your ics file at http://cal.outbackthunder.com has the event dates specified in 'local' or 'floating' times.
So the importing app will probably make the events be that time in it's timezone. 8am is 8am in all timezones (think of a travellers alarm clock - where they want to wake at 8m no matter the timezone they are in, vs a reminder to call their partner at 8am in the home timezone, where they'd then want it to adjust to the traveling timezone.)
Either add a Z and issue date-times in UTC, or add the TZID identifer of the timezone.
See https://www.rfc-editor.org/rfc/rfc5545#section-3.3.5.
See these examples in the spec:
Example: The following represents July 14, 1997, at 1:30 PM in New
York City in each of the three time formats, using the "DTSTART"
property.
DTSTART:19970714T133000 ; Local time
DTSTART:19970714T173000Z ; UTC time
DTSTART;TZID=America/New_York:19970714T133000
; Local time and time
; zone reference
Also try running your ics file through as many validators as you can find if you want the general public to be able to use the url. They tend to report slightly differently. EG: one says of http://cal.outbackthunder.com
DATE-TIME value in [DTSTAMP] must be specified in UTC time
Property [ORGANIZER] must be specified once
Related
Some events don't take place at any specific time and instead are meant to be valid for the whole day irrespective of the time zone the user is at.
For the sake of argument, let's say a system sitting on a server (up in the cloud) runs a job at 5 am and imports data from a different system between this run and the last (24 hours ago). The actual user sitting at his desk doesn't know when the job runs, the user only knows that they go to sleep at night, the server crunches all the entries for the day.
The next morning the user wants to see all the entries from yesterday (what ever the job produced) and they go to the app, pull up a calendar input selector and they pick the 5/26/2022 (today being 5/27/2022).
Assuming the developers followed best practices, the client will transform the date into it's UTC version and send it up through an API. Chances are, depending on where the user is located and the server is, there might be a mismatch.
I could send the date up without it being UTC or I could send a UTC date and try to adjust it back to local time so that I could then compare with the date on record (that exists without an actual time zone).
What I am asking is:
What's the more conventional answer to this particular problem?
Is the idea of a date without time or time zone just ridiculous?
Use UNIX Time. It will give you a timestamp that is universal no matter what timezone the user is in. You can then convert it into whatever timezone you want to.
The concern you describe is well solved/addressed by the ISO 8601 dates/time presentation protocol.
All modern software can read/write dates in ISO 8601.
In Unix machines, the correct command is date with option -I
-I[FMT], --iso-8601[=FMT]
output date/time in ISO 8601 format. FMT='date' for date
only (the default), 'hours', 'minutes', 'seconds', or 'ns'
for date and time to the indicated precision. Example:
2006-08-14T02:34:56-06:00
The RFC5545 spec allows DTSTART to be specified in UTC time. I'm thinking that's bad though, and could lead to be off by an hour. For example, where I live we honor DST, but parts of Arizona do not. So if the person in Arizona creates an event and it's just stored in UTC, won't I have a "one off" problem when DST switches on or off?
I'm thinking that I should always write the DTSTART and DTEND times with a TZID identifier.
No - the app or program displaying the time should convert the time correctly for the given day. It shouldn't matter what timezone you store the DTSTART in. What matters is correct Timezone transition for the given date by the program that's displaying the time.
So around the daylight saving switchover of a destination. two UTC times will map to the same destination time.
Aside:
There are some very big well known systems don't do Timezone setup for daylight saving zones in the best possible way, but that's a different problem.
DTSTART in UTC is bad mostly in the case of recurring events (especially with attendees). See Should event times specified in UTC while generating ICS files, to avoid issues with myriad calendaring applications for example.
For example, take this event:
210489449014070 Facebook Event / Graph API Explorer
This event was created back in September 2011. When it was created, it correctly showed Friday, November 11, 2011 11:11pm as the date and time of the event.
But now, it shows Saturday, November 12, 2011 12:11am as the date. This is also happening for future events, such as 426044564103401.
However, it's not happening for even e.g. in the current month like 330237680381087.
Which show the correct date (same as graph shows.) This one was created a few months ago.
My suspicion is that it's still applying the DST offset to the date. For example, right now, pacific time is 7 hours from UTC (because DST is in effect, thus PDT.) On 2012-11-04, DST will end and it will go back to 8 hours from UTC. It "falls back" in fall.
The date on the frontend of Facebook.com is showing as if it's still using the 7 hour offset (it's an hour ahead of what it should be.) My assumption/guess is that at 2012-11-04 02:00:00, it will begin showing the correct date. Hurray? But at that point, the dates that are correct now will probably show wrong (because it won't apply DST anymore.)
I'm guessing this means that internally, timezone-less events are now treated as "-07:00" or "-08:00" globally, based on the current UTC offset, rather than a date-relative one.
Do I have to pull all 186,272 events and update all of them to use timezone dates to fix this (also impacting frontend display to other users, and possibly impacting other parties that are interfacing with these events via FQL or etc.)?
Thanks for any help.
Was probably an issue when Facebook as migrating towards timezone-less events http://developers.facebook.com/roadmap/completed-changes/
I'm using GWT on the client (browser) and Joda Time on the server. I'd like to perform some DB lookups bounded by the day (i.e. 00:00:00 until 23:59:59) that a request comes in, with the time boundaries based on the user's (i.e. browser) timezone.
So I have the GWT code do a new java.util.Date() to get the time of the request, and send that to the server. Then I use Joda Time like so:
new DateTime(clientDate).toDateMidnight().toDateTime()
The trouble of course is that toDateMidnight(), in the absence of a specified TimeZone, will use the system's (i.e. the server's) TimeZone. I've been trying to find a simple way to pass the TimeZone from the browser to the server without much luck. In GWT I can get the GMT offset with:
DateTimeFormat.getFormat("Z").fmt(new Date())
which results in something like "-0400". But Joda Time's DateTimeZone.forID() wants strings formatted like "America/New_York", or an integer argument of hours and minutes. Of course I can parse "-0400" into -4 hours and 0 minutes, but I'm wondering if there is not a more straightforward way of doing this.
You could use java.util.Date's getTimezoneOffset() method. It's deprecated, but that's pretty usual for Date handling in GWT currently.
And AFAIR, you can specify something similar to "UTC+4" in Joda time.
Update: I looked it up, and it's "+04:00". Or use DateTimeZone.forOffsetHours() or even forOffsetMillis().
Gwittir (http://www.gwtsite.com) is a library for GWT that includes many cool utilities, like databinding, animation, reflection, and more. However, there are some other interesting goodies as well like the new Joda Time integration. If you have ever been frustrated by GWT’s lack of java.util.Calendar support, you’ll love this, as it makes it easy to do date manipulations in your applications.
otherwise, there are other ways to get timezone offset with + & -.
import java.util.TimeZone;
use: TimeZone.getDefault().getRawOffset()
this function will return the offset time in millisecond about your phone seeting. For Example, GMT-04:00 is equals to (-4)*60*60*1000 = -14400000.
After some operations to get the number which you want.
I have a similar but slightly different problem I think.
I actually need to store the clients timezone on the server, so that I can send out messages about dates stored in their calendar.
The dates are stored in UTC time in google app engine and of course I can store the current Timezone offset when creating the appointment. The problem comes when for instance I want to send out a summary email with a list of upcoming appointments in it. These appointments need to be offset with the correct Timezone adjustments for the client (Im happy to assume that they are still in the same timezone as when they created the appointment).
The real problem comes with Daylight Savings adjustments, so for instance I might have appointments stored for Saturday 30th October 2010 at 1pm (BST[GMT+60]) and Monday 1st November 2010 at 1pm (GMT).
So as you can imagine, I cant just use the current timezone offset (BST) as that would mean that the appointment on Monday 1st November would be listed as 2pm rather than 1pm (GMT+60)
It occurs to me that the best way to deal with this is just to store the timezone offset with each appointment individually, but I feel it would be much better to be able to determine the original timezone correctly in the first place, then just let java do the correct adjustments.
I'm developing an international software that act as a simple project management software and I'm facing a problem. This problem is about date/hour and time zone.
When a message is sent from one time zone to another time zone I can store the UTC (GMT) time in my database and then have it displayed differently according to the user's time zone. But this can't be done when I only work with date.
If I say a task is due to the 21st of March. Should I consider that this date can be 20 or 22 in some other countries ? What are your advices on this problem ?
Let's say a user in New York sets a due date for a project as "anytime on Monday 26 January". That means "anytime from 0600 Monday 26 January to 0600 Tuesday 27 January" in Brussels and "anytime from 2000 Sunday 25 January to 2000 Monday 26 January" in L.A.
So completing the task at 2100 on Monday 26 is fine in Brussels and N.Y., but too late in L.A.
One possible work around is never just work with the date. If the time is not specified, either set it for 0000 hrs or 2400 hrs on the date specified in the timezone of the user.
The users may have to deal with strange due dates/times, but speaking as someone who used to work internationally, it kinda goes with the territory.
You won't be able to achieve what you are trying to do without storing the exact time. You simply don't have enough information.
When you don't have a time, assume that the time is the end of business in the main locale for the application, then translate that time as you would any other time. An alternative would be assuming end of the business day in local time and adjust that to UTC. Everyone using the application would need to understand whatever default time assumption you make when the time is not specified. Coordinating to the main office may be best in a large enterprise whereas coordinating to local time may be best in highly decentralized environments where the local context is equally important.
If you aren't storing the minutes and seconds you have to assume that the date being entered is the desired date and not to any adjustments for GMT. Just put it in the database as is. The people on the west coast will have to assume that the due date is the same regardless of where you are in the world. If you want to adjust for time zones, you'll have to collect more information, like hour, minutes, and seconds.
The easiest solution would be just to display as the same date for everyone. The deadline would then effectively be midnight in the latest timezone.
Otherwise, decide what the default time of the deadline should be in the timezone the task was created in, e.g. 21st March 17:00 EST or 22nd March 00:00 EST and display that in the local timezone. The timezone difference will then push it into the previous day or next day accordingly for the viewer.
SQL 2008 allows for a Date datatype that does not have any time value associated with it. That allows someone to say I need this done by this Date, but I don't care if it is +/- several hours. If the date selected is 1/1/2009 but it happens on 1/2/2009 at 2AM their time, they probably don't care.
When the user needs something done by a specific date and time, like close of business on 1/1/2009 then you need to store it in a DateTime as UTC and convert it to local time client-side.
This will take much of the complexity out of indicating when something is completed, it'll either be completed near a specific day or by a specific time.
If you have a single instance of a DB, I would store all dates in the datetime timestamp of your DB server. If you are timestamping rows, consider GetDate() in T-SQL or as default value of the timestamped date column. Then you have your single reference point for all times. Consider UTC format there.
Then, all clients accessing the date do their own conversion into "local time" , which can be interpreted by things like : user preferences, date time stamp on client computer, etc.
Without knowing more, it hard to say exactly what the resolution is.
Your solution depends on your application and requirements.
I'd first store UTC + offset in your data structures, so it's easy to display for any timezone.
Most likely if a task or meeting is due at 12pm on 21/March in London then it will occur at 2130 on 21/March in Adelaide (+0930), but that is an application requirement not any sinister timezone related standard.
If you want the ultimate in flexibility, add a flag that can make the even due simultaneously in every timezone or at the same time no matter where you are (staggered) and show the event accordingly.
You might want to store the date in a from that is timezone aware. This will help you in your calculations. SQL Server 2008 for instance supports a datetimeoffset that does precisely this. Alternatively if you're using SQL 2005 with a bit of effort you can write your own SQL CLR data type to support this.