Does Transport Fever 3 Have Timetables?
Not in the base game. The developers considered timetables and left them out: day and night are only a visual choice, so towns do not travel more at rush hour. If you want them anyway, the Timetables mod by celmi, the author of the Transport Fever 2 timetable mod, was on the in-game mod hub from launch day. Without mods, four built-in settings keep a line evenly spaced.

“The game does not include timetables since the day and night options are a cosmetic choice rather than representing any change in the demand of towns.”
Four settings that do a timetable's job
Additional wait time
Set per stop in the line manager. Vehicles wait a little longer after loading or unloading, and the simulation uses that slack to spread the line's vehicles evenly. This is the closest thing to a headway timetable.
Departure mode
Load if available leaves with whatever is there. Full load (any) waits until one cargo type is full; Full load (all) waits until everything is. Only trains and ships tell the two full-load modes apart; every other vehicle waits for a full load either way.
Alternative terminals
When the usual platform is taken, a vehicle uses another one you have allowed. For trains the choice is made at the last signal before the station, so every alternative platform must be reachable from that signal.
Line priority
Trains and trams on a high-priority line reserve track further ahead, so a slow service stops cutting in front of an express on shared track.
Fixing bunched buses and trains
Bunching is the usual reason players look for timetables: three buses arrive together, then nothing for ages. Add a modest extra wait at one busy stop on the line first, and watch the line window's frequency figure settle. If a station is simply overcrowded, the station window shows unhappy passengers per line; the cure there is more vehicles, bigger ones or faster ones, not waiting.
On rail, bunching is often a signalling problem instead: trains queue because one of them holds a path the next one needs. The signals guide shows the layouts that stop it.
Platform length still matters
A train longer than its platform loads and unloads more slowly, and the vehicle and station windows warn you when that happens. Loading is already slower than in earlier games, so a short platform can undo any spacing you set. Specialized platforms, vehicles and warehouses speed it up; see the cargo specializations.