Converting Number from Scientific "E" Notation to GlideDateTime in ServiceNow

Today I hit a frustrating issue with a data import where a couple of fields which contained Unix date/time information were being received in scientific notation (e.g. 1.59855015616942E9).  How do we turn this into something we can use in ServiceNow?

Requirements

1. Convert a Unix Epoch timestamp, stored as number of seconds since 1970-01-01 00:00:00, in scientific 'e' notation (e.g. 1.59855015616942E9) into a GlideDateTime object containing the appropriate value (e.g. 2020-08-27 17:42:36).

Approach

Try not to tear out your hair figuring this one out!

Implementation

Make sure your number is actually a number (using the Number() function), then convert that into the number of milliseconds since the Unix epoch, then use the setValue() function on a GlideDateTime object to get a useful variable.

var evilNumber = '1.59855015616942E9';
var gdt = new GlideDateTime();

// Make sure evilNumber is actually a number by using JavaScript Number() function.
// Then multiply it by 1000 because GlideDateTime setValue() function expects the number
// of *milliseconds* from the Unix epoch, and ta-da!
gdt.setValue(Number(evilNumber)*1000);

// Print or otherwise use your shiny new GlideDateTime object:
gs.print(gdt.toString());

Enhancements

Write yourself a nice script include and a function to wrap this, then you can use it more easily in the future, and forget the pain you went through to figure it out in the first place... :-)

Disclaimer

As always, please test and evaluate anything you find in the community before adopting it for your own use.  Hope someone finds this useful, comments and suggestions welcome!