Latin, meaning the law of necessity is the law of time that is time present.
This is an old maxim which is used in modern times. It has been interpreted by many jurists and analyzed in many cases.
“The law of necessity is the law of time that is time present”.
Let us study each word one by one:
Lex– A system of law.
Necessitates– necessity, necessary, needed.
Est lex temporis: law of time, that is time present.
It means law of necessity is the law of time that is time present.
Keshar Sugar Works vs R.C. Sharma And Ors. 
The point for determination by this Full Bench is whether an appellant is entitled to have the period taken in preparation of a decree or formal order deducted from the period of limitation fixed for an appeal even if he has not filed an application for a copy of the decree or formal order.
Edited by Vigneshwar Ramasubramania
Approved & Published – Sakshi Raje
 11 May, 1950. AIR 1951 All 122