Q: how to convert DateTime into Unix TimeStamp in F#? is there a function / library / easy snippet doing that ?
I've found answers for Python for example, but not F# thanks
I've found the other way round here
http://tryfs.net/snippets/snippet-r6
open System

let toDateTime (timestamp:int) = 
    let start = DateTime(1970,1,1,0,0,0,DateTimeKind.Utc) 
    start.AddSeconds(float timestamp).ToLocalTime()


A: You should be careful because timestamp might be something else than int. However in .NET 4.6.x you should be able to use the functions referred to in the comments. 

Here's an example:
open System
let unix = DateTimeOffset(DateTime.Now).ToUnixTimeSeconds() //val unix : int64 = 1488254491L
let dt =  DateTimeOffset.FromUnixTimeSeconds(unix)  //val dt : DateTimeOffset = 2017/02/28 4:01:31 +00:00
dt.LocalDateTime //val it : DateTime = 2017/02/28 13:01:31

As ToUnixTimeSeconds and FromUnixTimeSeconds operates on DateTimeOffset, either work with that or convert back/forth to DateTime if necessary.
By the way I find it that in the .fsx file the intellisense is a bit flaky for these methods (but works). In .fs files it's OK. 
