When 'Tomorrow' Meant Today: A Calendar Bug, and How We Fixed It

If you asked one of our AI assistants to book something “tomorrow” recently and it didn’t land where you expected — that one’s on us. We’re sorry, and we’ve fixed it.

What happened

Our voice agents can book appointments on your TriLuna calendar. Last night, one of them did something it shouldn’t have: when asked to book an appointment for “11:30 tomorrow morning,” it booked it for today instead — at a time that had already passed — and then cheerfully confirmed it was done.

So the appointment was real. It just wasn’t where you’d look for it. If you went to check tomorrow’s calendar and found nothing, that’s why. It was sitting on today’s date, in the past.

That’s a bad combination: wrong result, plus a confident “all set!” that hides the mistake. We’d much rather a tool tell you it’s unsure than quietly do the wrong thing.

Why it happened

Two small failures stacked up.

First, the assistant resolved the word “tomorrow” to the wrong calendar date. It had today’s date handy, and when it went to book “tomorrow,” it reused today’s date instead of advancing it by a day.

Second — and this is the one that really stung — our booking system accepted the bad request. It had a check for dates in the past, but only at the day level. A time earlier today slipped right through, got booked, and returned “success.” There was no backstop to catch “you’re trying to book a slot that already happened.”

What we changed

We fixed both layers:

• The booking system now refuses to book the past. If a requested date and time has already elapsed in your timezone, it returns a clear error — “that time is in the past; today is X, tomorrow is Y” — instead of booking it. The assistant has to correct the date and try again before it can confirm anything.
• The assistant got clearer instructions about resolving relative words like “tomorrow,” and a rule to only tell you a booking is done after the system actually confirms it succeeded.

Both fixes are live in production now, and we verified them against the exact scenario that failed.

A note on timezones — and what’s next

This bug lived in the seam where “what time is it for you?” meets “what date does the AI think it is?” Timezones are a classic place for scheduling to go wrong.

ElevenLabs (the voice platform behind our agents) has recently added advanced timezone settings for agents — native support for telling an agent which timezone it’s operating in, so the current date and time are always correct for that context. It’s a welcome addition.

For now, we also run our own TriLuna-built scheduler that affixes the current date to the top of each of our agents — something like:

DATE & CALENDAR

Today: Friday, June 5, 2026 Tomorrow: Saturday, June 6, 2026

We’ll keep running our own date logic until we’ve confirmed the new ElevenLabs timezone handling makes it redundant. We’re not going to flip off a working safeguard on the assumption that a newer one covers every case — we’ll verify first, then simplify.

The takeaway

A tool that’s wrong and sounds certain is worse than one that admits doubt. The real fix here wasn’t just teaching the assistant to count to “tomorrow” — it was making sure the system underneath says “no” to something that can’t be right, so a confident voice can’t paper over a bad booking.

If you were affected, we apologize. Thanks for your patience while we tightened this up.