Redeeming A Tithe, Different Times

[millerbr19]

So I ran across this website through a form talking about the redeeming of tithe.
I know that Leviticus says that we're supposed to add a fifth of the value to it, but I'm still confused.
According to another website it tells me that I should multiply by the skipped months... I have a hard time accepting that because I don't get paid by the month, I get paid every week.
Should I multiply my tithe by the week since I get paid by the week?

[4WD]

There is no command within the New Covenant for the tithe.  That was basically the means under the Old Covenant for supporting the Tribe of Levi who were not given land and the means of supporting themselves.