With Windows 10 version 1703, Microsoft introduced built-in ICU support, allowing applications to use the system provided ICU instead of bundling their own. By leveraging this, Xojo now benefits from automatic updates, a reduced app footprint, and improved compatibility with the latest Unicode and locale data.

Which parts of the framework use ICU?

One of the main areas where ICU is used is the DateTime class, which includes Locale and TimeZone support. This helps with formatting dates and times and handling timezone differences reliably. ICU is also used for number formatting and string manipulation, particularly when working with characters like emojis and other complex Unicode symbols.

What benefits can be observed?

• Fewer DLLs
• 45MB smaller app sizes
• Faster execution times, i.e. DateTime.Now is roughly 10% faster
• Daylight saving time no longer requires a rebuild of your Xojo app

What are the new requirements?

As mentioned, Windows began including prebuilt ICU libraries starting with Windows 10 version 1703, so your apps won’t run on earlier versions. However, if you’re using Windows Server 2019, you’ll need to be on at least version 1809.

Conclusion

By shifting to Windows’ built-in ICU libraries, Xojo has eliminated the need for manual ICU updates and reducing app file sizes. This change means your apps will always have the latest updates for date/time, locale, and character handling, thanks to Windows updates.

William Yu grew up in Canada learning to program BASIC on a Vic-20. He is Xojo’s resident Windows and Linux engineer, among his many other skills. Some may say he has joined the dark side here in the USA, but he will always be a Canadian at heart.

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Date

• Mutable (you can change any of its properties without having to create a new Date)

On the surface this sounds great, but you can get into some ambiguous Dates depending on the order of operation, for example:

Dim d As New Date(2019, 2, 28)    // February 28, 2019
d.Day = 31   // February 31, 2019?
d.Month = 3

In reality since February 31 is not a valid date we have to coerce it into one, in this case we roll over as 3 days into March, so after the Day has been set to 31 the actual date is now March 3, 2019, probably not what the user intended.

• Uses local TimeZone (no way to use a different TimeZone)

Consider living in California and trying to determine the time in New York. With the Date class you’d have to calculate the time offset yourself.

• Uses current locale for date string formatting (no way to use a different locale)

If you’re trying to display something for your French or Spanish speaking compadre and you’re on a English speaking region, you’d have to format the date yourself.

• Fixed GMTOffset (no understanding of daylight savings rollover)

The GMTOffset is always the current TimeZone offset, unless its has been specifically set in one of the Date constructors.

DateTime

• Immutable (none of its properties can be modified, you’d have to create a new DateTime)

While this may seem more restrictive, this provides protection against setting ambiguous dates. You can use DateInterval and/or DateTime.AddInterval to manipulate the date which is returned as a new DateTime object.

• TimeZone savvy

Each DateTime object can be associated with a different TimeZone. For a list of all the supported TimeZone names, see:
https://docs.oracle.com/cd/E41183_01/DR/ICU_Time_Zones.html

• Date formats are locale savvy

Instead of being tied to presenting a date string in the current locale, you can specify a different locale in which to display your formatted date string.

• Daylight savings aware

A TimeZone is always associated with a DateTime object (if none is specified then the current TimeZone is used), you can use the TimeZone.SecondsFromGMTOffset to determine if the Date is in daylight savings.

Daylight savings boundary behavior

When daylight savings end on November 3, 2019 at 2:00am the date will fall back one hour so we really are on November 3, 2019 at 1:00am. So how does Xojo handle the case where a user sets the date to be November 3, 2019 at 1:00am? Is it just before daylight savings or after? The answer is, after, with the TimeZone GMTOffset adjusted accordingly.

For more information about the new DateTime class, make sure to check out the documentation page on it: http://documentation.xojo.com/api/deprecated/date.htmlTime