This is the Stardew_Save_Backup mod which automatically takes your save folder and zips it into %appdata%/StardewValley/Backed_Up_Saves for later retrieval upon launching SMAPI! This is especially usefulif you are modding/using mods and don't want your characters to be messed up, or if your game happens to crash form some odd reason, or you lose your save file!
You can also keep as many back-ups as you desire, and are only limited by the hard drive space on your computer!
If you ever want to get back to your old save files, simply open up the desired .zip folder with any archival tool such as windows file manager or .7zip and you can now access your old save files!
I'm open to improvements for this mod as of writing this. If so desired I will research adding functionality for when your character goes to bed that it will back up your save files, or doing a backup after x amount of days that have passed in game.