How do I check the memory usage from a certain time in macOs? I had a website which was using massive amounts of memory on my MacBook but I was unable to take  a screenshot of the total memory usage from Activity Monitor to file an issue with the website. Is there any way I can see the log of the Activity Monitor from a specific time?
No, Activity Monitor does not store historic information about memory usages anywhere.
The system also do not by standard log such information into log files or databases or anything like that. So the information you seek is gone now, I'm afraid.