There is a limited time period to respond to a subject access request. How long depends on a couple of factors. Let’s start at the beginning. When you receive a subject access request, you need to be able to verify the identity of the person making the request. You can view my previous blog about verifying their identity here. You cannot hold up verifying the individual’s identify to delay a response. Frequently an individual will include a means to verify their identify as part of their request. Once you have verified an individuals identity you have a calendar month to respond to the request. 
If your requests is received on the 5th July, you have until the 5th August to respond. If there is no corresponding date in the following month, you have the last day of the month the respond. for example, you receive a subject access request on the 31st January, you have until the 28th February (29th in a leap year) to respond.
Where the response day falls at a weekend, you have until close of play on the next working day to respond.
There is he ability to extend the timescale and I’ll cover this in the next blog.