BUGFIX: fixing NaN issue on IE, Safari and Firefox #7

[IngridRegina]

This fixes the NaN problem on Safari, Internet Explorer, Firefox and Edge (it should resolve issues #7 and #3). It is worth noting though that these browsers do not support all the date formats that Chrome supports(you can see that some of the events from myEvents array are not showing). For example they don't seem to like month names, so instead of February/15/2020, 02/15/2020 should be used. So it should be made clear that the formats that are not supported shouldn't be used.

[edlynvillegas]

Hello @IngridRegina! :hugs:

I really appreciate this because I really need some help especially in this Safari thing issue.

I'm currently working on some upgrade like adding themes, methods and events, and I rewritten the code to make it more optimized. So the structure of the code changed a bit, that's why I can't merge this pull request.. But I will look into it once I'm done. :smile:

Regarding this NaN issue, I am now testing it to many browsers except Safari because I am using windows only.

Btw, thank you for this! Looking forward to work with you