The time for a capactior in a circuit to:
A.) charge to (1-e-1) % of the difference between current charge and the maximum charge. (63%)
B.) discharge to e-1 % of the current charge. (37%)
As a general "rule of thumb", a capacitor can be considerd fully charged/discharged after 5 time constants. The formula for a capacitor's time constant is:
t = RC
Where R is the resistance of a circuit, and C is the capacitance of the capacitor.