Need calendar synchronization set up across company tools

Our company relies on several different scheduling and calendar tools across departments, and right now none of them talk to each other properly. A meeting booked in one system does not appear in another, and every reschedule or cancellation has to be repeated by hand in two or three places. This wastes time and regularly leads to confusion and people showing up for meetings that were already moved or cancelled. We need a specialist who can connect these calendars into one coherent setup so everyone sees the same up-to-date schedule no matter which tool they open.

The main requirement is a single, reliable source of truth for meetings: when an event is created, moved, or cancelled in one calendar, that change should propagate automatically to the others within minutes, without anyone re-entering details manually. Our staff work from several cities and time zones, so the solution also needs to display meeting times correctly for each person's local zone.

We would like the specialist to review our current tools, propose the most stable way to link them, and implement the setup with clear documentation so our own IT person can maintain it afterward.

What matters most:
— automatic two-way updates on reschedules and cancellations
— correct time zone conversion for every employee
— no duplicate or conflicting events
— clear instructions for future maintenance