I think it can depend on your plan too. Vodafone's off-peak hours are:

1) 19:00 - 08:00 with a contract

Daytime rates apply 8am-7pm, Monday to Friday. Evening rates apply 7pm -
8am, Mon. to Fri. Weekend rates apply all day Saturday and Sunday.

2) 19:30 - 07:30 on PAYG.

You'll pay daytime rates 7:30am - 7:30pm and evening rates run from
7:30pm - 7:30am Monday to Friday. And you get weekend rates all day
Saturday and Sunday - no matter what time it is. We count a day as
midnight to midnight.

(Quotes from the appropriate T&C pages ion the Vodafone web site.)