Javascript ES6, 73 67 bytes
setInterval(_=>alert(new Date().toTimeString().substring(0,8)),1e3)
Works with my current time settings (which have not been changed for some time, thank you), at least.
setInterval(_=>alert(new Date().toTimeString().substring(0,8)),1e3)
Works with my current time settings (which have not been changed for some time, thank you), at least.