I try to use firebase db, I found very important restrictions, which are not described in firebase help or FAQ.
First problem is that symbol: dot \'.\' prohibited in
Personally, I found a simple and easy hack for this same problem I encountered
I took the dateTime string and convert it using replace('/','|')
dateTime string
replace('/','|')
the result will be something like this 2017|07|24 02:39:37 instead of 2017/07/24 02:39:37.
2017|07|24 02:39:37
2017/07/24 02:39:37