Swift Date Timezone
Swift Date Formats

How dashing you look; is the key factor when you have Date[s] 😜. Same goes with our Date also when we are in the Swift arena. Although dashing may not be the proper term, rather presenting thyself is more appropriate. DateFormatter comes into play on this occasion. Swift Date formatter is one of the confusing item that we pass by regularly. At the end of this blog post we will make ourself dashing when it comes to Swift Date formatter 😎.

Background:

When parsing ISO8601 internet dates, always use ISO8601DateFormatter; If you can't because your API format doesn't fit ISO8601 and you still absolutely need to use a custom dateFormat, then be sure to also set your dateFormatter.locale to the special value Locale(identifier: 'enUSPOSIX'). Formatting user-visible dates for your UI. In the previous article in this series on working with dates and times in Swift 5, we looked at three key structs for date and time programming in Swift: Date represents a single point in time, using a format that can easily be translated into just about any calendar and time-reckoning system: a number of seconds relative to the start of the Third Millennium (January 1, 2001, 00:00:00 UTC).

What type of formatter are you, DateFormatter?
Preparation of using DateFormatter.
Graphical representation of DateFormatter.
DateFormatter says: “Do you mind, homie”?
Defining Skeleton of DateFormatter

DateFormatter

As we can guess from the formatter keyword of DateFormatter, that it formats the Date into some representing way and that way is textual representation. It turns out that we can also construct Date from a textual representation also. So basically DateFormatter is the converter of Date and textual representation.

We already talked in details on Date on our love or hate talk 😉. Free fell to pay a visit.

Pre talk of DateFormatter()

We have to set the following two, after initializing and before using DateFormatter.

set the locale for the DateFormatter. If not set, then it will use the system provided locale.
set the format style. Now there is two way to do this.
- By setting the dateFormat property.
- Or by setting the dateStyle and/or timeStyle. One or both need to be set based on the provided input.

Such as:

On the following code we will format some random date.

We can always visit the First blog post to read more about ReferenceDate.

Pictorial view

If we want have a pictorial view:

Pretty self explanatory. Though last two methods need some attention. .string(from:) converts Date to String, on the other hand date(from:) converts String to Date.
And also date(from:) returns an optional Date, Date?.

yo homie

Localization is a must have for DateFormatter. Because without knowing the locale the formatter can not represent the Date on String or make a Date from String formatted date.

In a nutshell: Local is basically a structure; which provides necessary formatters and symbols, those are define for a specific Locale. Example $ is the currency code on USA and for UK it is £. On Sweden it is common to have , as a decimal separator example 123,23 where on Asia it is .example 123.23. Local provides us all those and also many others. May be on some future post we will have some more talk on Locale.

Now back to our Localization discussion on Date: So on worst case scenario we did not set the locale for our DateFormatter, as a result the DateFormatter will use the system-provided-locale.

And we can imagine the consequences: In some distinct future there is a probableDate related bug which happens to some user; if lucky we know that it is a group of people having this bug. Too difficult to find out among such possibilities.
OH Come on, we are better than this. We always know, how our program gonna behave. We don’t let other programs to do some uninvited operation on our own program; thats become a guess based bug for us.

Always set the `locale` just after `DateFormatter` initialization and must be before using that `DateFormatter`. Setting the `locale` should be the very second line of our `DateFormatter` task.

dateFormat vs dateStyle with/without timeStyle

To retrieve or relinquish Date, we need to have a skeleton based on which we can get and set the date.
There are two ways to achieve this.

One was is to respect the locale and set the formatter style by defining dateStyle and/or timeStyle.
Another way is to use a fixed format irrespective of locale.

For the next section discussion, I am confident that we already set the local for our Date instance. 🧐

Let’s talk about the first option first.

`dateStyle` and `timeStyle`

Example is the best way to start. You can find the date format by countries on wikipedia. What does this list means? It means, a specific country follows a/multiple fixed format for Date. Let’s pick Iceland and Panama, as our example. We can list the following:

Iceland: dd.mm.yyyy
Panama: Short format: mm/dd/yyyy and Long format: d de mmmm de yyyy

Now dateStyle and timeStyle both are enum. Having values like none, short, medium, long, full.
So after setting the corresponding locale, Iceland or Panama, if we set the dateStyle according to the value such as shortlong then we should be able to represent the Date into String and vice versa using our dateFormatter.

We are skipping the TimeStyle here.

Now the good thing about using the dateStyle is: the end user is happy, because he/she is seeing the comfortable date presentation. The user need not to look for another round to figure out the date.

`dateFormatter`

But the happy story will not be same for all the requirements. In some times we need to have a fixed format of date regardless on the user Locale. In this case we have to use the fixed-date-formatter, dateFormatter.

For dateFormatter we will use a fixed String , EEEE, MMM d, yyyy, for identifying the date-string. EEEE stands for day name. There is the ref section at the bottom if we need some help with the symbolic representation of Date component.

Just small note: as the 5.11.2018 does not have a format of EEEE, MMM d, yyyy, thus calling the formatter.date(from: '5.11.2018') yields nil.

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When to use which one

The choice among dateFormat and dateStyle is actually based on requirement.

When the requirement is to have the user preferred way or respecting the user locale then we must use dateStyle.
On the other hand if the requirement is some fixed format irrespective of user’s locale, then we have no other choice but to use the dateFormat.
Another case we have to consider, when the format is locale to a group of people and also the format is fixed then again we have to use dateFormat.

Swift Date Timezone

So on the next time we gonna work with date, we

Swift Date Formats