c# - How to parse relative time?

Question

This question is the other side of the question asking, "How do I calculate relative time?".

Given some human input for a relative time, how can you parse it? By default you would offset from DateTime.Now(), but could optionally offset from another DateTime.

(Prefer answers in C#)

Example input:

• "in 20 minutes"
• "5 hours ago"
• "3h 2m"
• "next week"

Edit: Let's suppose we can define some limits on the input. This sort of code would be a useful thing to have out on the web.

Answer 1

A Google search turns up the parsedatetime library (associated with the Chandler project), which is designed to do exactly this. It's open source (Apache License) and written in Python. It seems to be quite sophisticated -- from the homepage:

parsedatetime is able to parse, for example, the following:

* Aug 25 5pm
* 5pm August 25
* next saturday
...
* tomorrow
* next thursday at 4pm
* at 4pm
* eod
* in 5 minutes
* 5 minutes from now
* 5 hours before now
* 2 days from tomorrow

Since it's implemented in pure Python and doesn't use anything fancy, there's a good chance it's compatible with IronPython, so you could use it with .net. If you want specifically a C# solution, you could write something based on the algorithms they use...

It also comes with a whole bunch of unit tests.