I highly discourage doing this project. There are very good and stable solutions with lots of configurabilty that will integrate in whatever intranet you already have.
Though, if you really have to do this, you might want to buy a desktop scanner with a driver which writes the barcode to std-in. All you have to do is put a terminal somewhere with that scanner (I would go for a Raspberry Pi) and open up the website.
As database, you really should use something stable. Use an enterprise product. Use a licensed MSDB or Oracle DB.
As DB and application servers (separated!) you should use virtual servers which run on clustered hosts (e.g. MS Failover Cluster).
Everything else is just writing some application which inputs data into some database. You probably should add a GUI for the employees and employers as well. I highly recommend using ASVS, as well as other OWASP projects, in order to secure the whole system. You might want to join the discussion in this question.
Also be very strict about who can access the database. You don't want your employees to "fix" their timestamps themselves...