Based on your question and the conversation in solution 1 I would recommend storing the date (and time) either in
column, depending on the resolution you want to have.
In other words I would convert the unix timestamp to a MySql native date type when storing the data in the first place. This helps you when you want to compare dates, calculate using them etc. If you leave it in unix format, you always have to remember to convert it when using and with greater amount of data this also causes some CPU overhead.
To select proper date type, have a look at MySQL :: MySQL 8.0 Reference Manual :: 11.2.2 The DATE, DATETIME, and TIMESTAMP Types