Push notifications

I'm trying to send a notification but I'm unable to

TL;DR

Developers are having trouble selecting a date when "now" is chosen, possibly related to a null date error. The system requires a 24-hour format for time, but only accepts 12-hour. They're also unable to schedule notifications, receiving a "d is null" error when trying to send now.

when I try to send now I get a "d is null" error, what does it mean?