You'll need an online tool to find the difference, like ours here at Converte Online, just enter the start and end date and you'll get the difference in days, years, months, hours, minutes and seconds.
Now if the intention is to do this in Excel, for example, you must use the functions of Excel itself, in this case there is a function that just needs to change the parameter and it returns different results.
The function in question is DATADIF, in it you must inform the initial and final date and which result you want, whether days, months or years, see some examples:
Difference in Days
, note that, the "D" causes the result to be in DAYS.
Difference in Months
, in this case we use the "M", which is the representation of Months.
Difference in Years
, last but not least, the use of the "Y", which indicates Years.
