DISCLAIMER: This post is purely a personal opinion, not representing or affiliating my employer's.

PaaS (Platform as a Service) like Azure Functions is a fully-managed service, so we don't have to do maintenance efforts. This often implies that there are something we can't configure. One of these limitations is locale. Throughout this post, I'm going to talk about handling locale in Azure Functions. Let's have a look at the following date format. How can you interpret it?

11/12/13

Depending on our culture (or locale), this can be translated in different ways:

Korean (ko-KR): Dec. 13, 2011
US English (en-US): Nov. 12, 2013
AUS English (en-AU): Dec. 11, 2013

If we develop a new application, we follow ISO 8601 format not to be confused so that in general we use the date/time format like yyyy-MM-ddTHH:mm:ss.fffzzz. However, not every system follows this format. In many integration scenario, we have to deal with legacy systems that uses localised date/time formatted values. Even worse, if we handle those legacy data on the cloud like Azure Functions, this must be properly handled; otherwise it will be in trouble. Let's have a look at the code below.

{
  "date": "11/12/13"
}

If we use the payload like above, how does this date format get parsed?

https://gist.github.com/justinyoo/f98f86536560c9b99cedbdcf48cadb4c#file-locale-default-cs

If your dev machine's default locale is set to ko-KR, it will display like:

Input: 2011-12-13T00:00:00.0000000+09:00

If yours is en-AU, then you will see like:

Input: 2013-12-11T00:00:00.0000000+11:00

OK. What if we deploy this code into Azure Function instance?

Input: 2013-11-12T00:00:00.0000000+00:00

As you might have expected, it follows the US locale, en-US. If our data only deals with Australian locale, ko-KR? There's no way to change the locale of an Azure Function instance. In other words, we should handle this in the code level. Fortunately, we have Thread.CurrentThread.CurrentCulture, so we need to change this value. Let's have a look at this code below:

https://gist.github.com/justinyoo/f98f86536560c9b99cedbdcf48cadb4c#file-locale-en-au-cs

Like the code above, we can simply add one line that changes the default locale, en-US, to en-AU. Once deployed, it returns the expected result.

Input: 2013-12-11T00:00:00.0000000+00:00

Easy, huh?