It is important however, to check out with any organisation you are interested in volunteering for, what time commitment they have in mind. You will need to work out how many hours you will volunteer for and for how long you wish to volunteer.
How much time you give is up to you. You can find a short placement that only takes an hour a month - for example, if you work as a befriended, this could take no more than a few hours of your time.
Basically, you can volunteer at any time for any length of time, day or night. While most volunteering opportunities might take place in office hours, you can volunteer at evenings and weekends too, depending on what you want to do.
Be realistic about how much time you can give. Don’t make long term commitments unless you are sure you can fit it in around any other obligations, such as friends and work, that you may have.