To find an answer to this question you need to know the location of interest and check the business opening hours.
For example, in the United Kingdom, FedEx doesn’t operate on Sundays. During public holidays it is advisable to check the opening hours as these are subject to changes year by year.
In the USA FedEx is closed on Sundays. However, the online tool is always functioning.
You need to check the opening hours for other countries as there could be celebrations that you might not be aware if you live in the USA, for example.
If you need to find out about the shipping and business hours in other locations worldwide it is advisable to contact the customer service through email or by phone and inquire about the specific location.