Why do the times change on my appointments when I travel to a different time zone?
Posted by Chris McSorley on 15 January 2013 10:27 PM

We get several questions from customers who travel asking why their appointments appear to change times when they go into a new time zone.  For instance, you might set up an appointment at 3pm in New York (EST), then fly out to California (PST) only to find that your appointment is now at 12pm.  Why is that and is there anything that can be done about it?


The Basics

To fully understand what is really happening and why, it's important that we first cover a few basics so that we are all speaking the same language:  

  • Calendars ≠ Alarm Clocks
    • It's important to understand that calendar systems, such as Pocket Informant, are inherently different than alarm clocks.  Alarm clocks care about what time something occurs while calendars care about when something occurs.  Alarm clocks don't know about specific points in time, they only care about what time it is "here".  Meaning, if you set an alarm for 6am, it will go off at 6am no matter where in the world you are.  Conversely, calendar systems care about specific points in time.  Meaning if you set an appointment for January 15, 3:00pm, what you are actually saying is that the event occurs at January 15, 3:00pm in your time zone (unless you have explicitly specified some other time zone).
  • Time Zones are really just "labels"
    • Since calendars care about specific points in time, we need a mechanism to inform the calendar when the event is that we are scheduling.  Time zones are geo-political labels that we have all agreed on to help us with two things
      1. Help us describe specific points in time no matter where we are.  So, while people in New York would call a specific point in time "January 15, 3:00pm EST", people in California would call that same exact point in time "January 15, 12:00pm PST".  In both cases, they are talking about the same exact point in time, they simply have a different "label" for what they call that point in time.
      2. Help us describe the "time of day" consistently across the world (meaning no matter where we are, we all understand that "5:00am" is early in the morning). 


It's important to clarify the above points because when you travel from one time zone to another, it might be tempting to think that Pocket Informant is "changing" or even "messing up" the times on your appointments.  In reality, absolutely nothing as happened to your data - Pocket Informant does not alter the actual data in the database simply by changing time zones.  What does happen, however, is that Pocket Informant changes the "label" that it shows you for all of your appointments.  Phrased another way: Pocket Informant is not changing when your appointment occurs, it merely changes what it calls that point in time now that you are in a different time zone.



After reading the above, the next logical question is often "why don't calendars work more like alarm clocks?  I don't want to think about time zones, I just want to think about times".  While on the surface this might seem like a good idea, it actually creates a host of problems.  Here are just a few issues to consider:

  • Constant mass updating of data is error-prone - Ironically, by "keeping the time the same" when you travel, Pocket Informant would actually have to change your underlying data every single time you change time zones. Since events are stored as a fixed point in time (say 3pm CST), when you travel, it now has to update that event to occur at 3pm PST - a different point in time than you originally specified.  Plus, if you have any alarms for your appoints, all of those would have to be rescheduled as well (they were originally set to fire 15 minutes before 3pm CST, now they must be scheduled to fire 2 hours earlier).  This is especially problematic for folks who live near a time zone border.
  • Many appointments rely on when it occurs, not what time - consider conference calls, for instance.  Suppose you have to be on a call every Monday at 3pm EST.  However, this week you fly out to California.  If your calendar changed your conference call to 3pm PST, you would completely miss your call (since you would be dialing in at 6pm EST).  
  • Communicating across time zones - suppose you are on a business trip in a time zone that is several hours different than yours. On your calendar, you have an event for when your son back at home is taking an important test.  If you want to be sure to call him right after the test, you most certainly would not want the time of that event to change when you travel.
  • Meeting Invites - When you send a meeting invite to someone, a copy of that event is stored in their calendar.  Neither of you want that shared event to change times simply because one of you traveled to a different time zone.
  • We share calendars - more and more we live in a connected world where we share calendars (between family members, co-workers, friends, etc).  For instance, if you sync with Google, other people can subscribe to your Google calendar and have it appear on their device.  Google doesn't support floating time zones currently, so Pocket Informant would be in the business of having to update your Google calendar with the new local time for all your floating events every time you traveled (and then sync down to every person who shares your calendar - at which point everyone sharing your calendar sees all of your events changing times when you travel).  Support Google Calendar did support floating time zones - then you would have another problem...people sharing your calendar would see your events in their time zone while you see it in yours -- thus you would each be seeing the same events at different times.  It's a far cleaner approach up front to simply specify the exact point in time that your events occur rather than specifying the time of day they occur. 


I travel a lot - can Pocket Informant help?

While this topic is often a source of confusion when interacting with just about any calendar app, we are pleased to say that Pocket Informant has put in place some convenient features to help keep your time zones and appointments straight.  Starting with version 2.0, Pocket Informant now allows you to control the time zone display at 3 different levels - but it's important to read the details of each setting to determine if these settings will make PI behave the way you expect:

  • App Level Time Zone - You can lock Pocket Informant to a time zone at the app level (Settings Tab -> General Settings -> TimeZone).  When you set an app-level time zone for Pocket Informant, it will display all tasks & events in the time zone you specify regardless of what time zone your device is set to.  Also, any new events or tasks that you create will default to being created in this time zone (again, regardless of your device's time zone).  Likewise, alarms attached to your events will be set for this time zone as well.  Pocket Informant will not constantly update your alarms to the "current" time zone as you move around.  You are effectively telling Pocket Informant to always pretend like it is in a single time zone regardless of where you are.  Thus, suppose you lock PI to CST and create an appointment for January 15, 7:00pm with an alarm to fire 15 minutes before the event.  The alarm is scheduled for January 15, 6:45pm CST - and that is when it will fire no matter what time zone your device is in.  This can be a source of confusion because when you fly out to a different time zone (say, PST), Pocket Informant will still display the event as occurring at 7pm because you've locked the display to show you everything in CST.  And again, if you create an event while in the PST time zone, PI will still default to creating that event in the CST time zone.  And likewise, the alarm you set for your original event won't change to PST - it will still fire at 6:45pm CST the way you originally scheduled it.
  • Per Calendar Time Zone* - Instead of locking the entire app to a specific time zone, you can elect to lock a single calendar to a given time zone (Settings Tab -> Calendar Settings -> Manage Calendars -> Choose a calendar).  This feature is extremely convenient if you travel to a particular time zone on a frequent basis.  Suppose you live in the EST time zone, but you travel to PST regularly.  You can lock one (or more) of your calendars to PST.  Thus, no matter where you are, you can schedule an event on your "PST Calendar" and PI will create, edit & display those events in PST even though the rest of your calendar data will be appearing in the local time zone.  Additionally, alarms would also be created in the PST time zone.  As an added benefit, when you look at the details of an event on this calendar, PI will show you the start/end time of that event in the time zone of your calendar and the local time zone if it's different.
  • Event Time Zone Picker - You will notice that as you create or edit events, Pocket Informant has a Time Zone button right next to the time field.  This feature is primarily there so that you don't have to do time zone calculations in your head when creating an event that will occur somewhere else.  It does not cause Pocket Informant to always display that event in your calendar in the specified time zone - it is merely to offer assistance in entering the time.  However, if you do explicitly specify a time zone using this feature, Pocket Informant will remember that and the next time you edit that event, PI will default using the time zone you specified before.  You will also see the event listed in your specified time zone AND the local time zone when looking at the Event Detail screen.

*Note: this feature currently only works for "Pocket Informant calendars", not iOS calendars.  "Pocket Informant calendars" are those that are stored in PI's database and perhaps synced with an online service such as PI Online or Google. iOS calendars are what you get when you turn on "iOS Events" in Accounts settings to display the device's calendar data in PI.


Future Plans

WebIS typically doesn't commit to implementing specific features prior to releasing them.  However, we are always looking for ways to improve Pocket Informant and make it easier to use - including the subject of time zones.  We are currently evaluating the feasibility of implementing a couple different features that we think would be unique and helpful for frequent travelers.  In addition to those, we have also been considering a feature supported by some calendar systems known as a "floating time zone".  While floating time zones have the potential to create some unintended side effects when not used properly, there are some use cases for them that are extremely compelling (such as the case where you might want to schedule an event for Jogging every morning at 5am no matter what time zone you are in).  Keep an eye on the "What's New" section with future updates to Pocket Informant on the App Store.

(16 vote(s))
Not helpful

Comments (0)
Post a new comment
Full Name:
CAPTCHA Verification 
Please enter the text you see in the image into the textbox below (we use this to prevent automated submissions).