544. ab

Question 1

ab: as of

As of today, the new law becomes effective.
As of the effective date, the new rules will apply.

Answer 1

Ab heute tritt das neue Gesetz in Kraft
Ab dem Stichtag gelten die neuen Regeln

Question 2

ab 1990: as of 1990

As of 1990 the company used a computer for its accounting.

Answer 2

Ab 1990 verwendete die Firma einen Computer für die Buchhaltung