How do I get the Arduino to record what the state was a minute ago?

I am trying to do a project that reads temperature and CO2 gas levels and compares it to what it was a minute ago. So basically, check the CO2 and temperature once a minute, move it to "past data", compare new current data with old data.

I have searched all through the internet but I can not find a way to do this.

Please could I have help with this?

Are you making samples once per minute or are you doing it more often than that? The first option is just to compare this reading to the previous reading. If you're making samples every second, then you need to store 60 seconds (individual measurements) to see the one from a minute ago.

If you are sensing more than once per minute, store the values in a circular array.