Calendar Busy Time Mirror for Consultants

Mac app that mirrors busy time between client and personal calendars.

Consultants in several client Microsoft 365 accounts copy events by hand to avoid double bookings. This tool mirrors busy time on Mac.

The evidence

Score: 40 out of 100

BusyCal, an established Mac calendar app, already does on-device busy-time blocking across calendars for $49.99 once; free sync tools also exist.

i have to go manually every time and mark the same time as busy on each calendar separately
r/ExecutiveAssistants on Reddit

Getting my work calendar to stop double-booking me is a solid 4 hour weekly drain I'd happily hand over.
r/artificial on Reddit

if a client booked on rula, the time wouldn’t get blocked anywhere else and it would lead to double booking all the time
r/therapists on Reddit

BusyCal (Busy Apps): Lists 'Cross-Calendar Time Blocking' and busy-only blocks on other calendars, works with Microsoft 365; we could not confirm how it handles locked-down client tenants.
Unified Calendar Sync (Mac App Store): Menu bar app that copies events from iCloud, Exchange and CalDAV into one calendar, all processing local; brand new and unproven, but it shows how easy the on-device build is.
OneCal: Cloud sync with 10 000+ customers and consultant testimonials; its pricing page says nothing about client IT approval.
CalendarBridge: Says Microsoft 365 tenants may need admin approval and supplies IT approval documents; its own blog says calendar-link (ICS) feeds may update only once or twice a day.
OGCS (Outlook Google Calendar Sync): Windows only, supports free/busy-only sync; no Mac and no iPhone.
SyncThemCalendars: Cloud sync for single users; says nothing on blocked work accounts.
Reclaim.ai: Time-blocking planner first; sync is a side feature with caps.
Cal.com: Booking page with conflict checks; does not mirror busy blocks into your other calendars.

The promise 'client IT approves nothing' is untested: tenants strict enough to block cloud apps may also require managed devices, which blocks Apple's own Calendar, leaving a thin segment.
Many consultants join clients as guests with no client mailbox or calendar, so there may be nothing on the device to mirror.
Demand is thin: 26 of 50 pains mention calendars, only 8 are about sync and 3 near this job; the top quote is a builder, not a buyer.
A $10 monthly subscription passes BusyCal's $49.99 one-time price in 5 months, and the free Unified Calendar Sync is already in the Mac App Store.
Mirroring one client's busy times into another client's calendar may breach confidentiality terms, and a bug that deletes events harms the consultant's standing.

Businesses struggle with time-consuming manual scheduling, double-bookings, and client no-shows that waste resources and lose revenue.

Service businesses and professionals

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