Time ScheduleField, Best practice

No code, but I looking for best practice, things to consider. I am doing an i18n scheduling app. I have a depart time (tA) and arrival time(tB). Often tB will be the next day. I want to display the times on iPHONE, ANDROID as a tick down clock for when tA departs and tB arrives. These are daily scheduled events and I dont want Date field. Example tA is 5:23AM and tB is 3:23PM. or... tB is 01:23Am the next day. I also want to format this number as a Military string like 01:23 or 22:33 or as a normal time string.

My question, What sort of field type should I use for this kind of Time stamp? I was thinking of just an INT of seconds but I wanted to get some feed back. The use case is something like when a train leaves a station or a scheduled flight. My software platform will be... Swift, Kotlin, GoLang, Dart, and JS/Polymer. just looking for comments.