Can Excel send date reminders?

No — Excel by itself cannot send reminders. It has no background process: formulas and conditional formatting only update when the file is open, so a spreadsheet can show that a date is near, but it will never email, ping or notify anyone. The 'reminder' only works if someone happens to open the file in time — which is exactly how expiry dates get missed.

Workarounds exist, with honest trade-offs: Power Automate can email you based on an Excel table in OneDrive (works, but it's a separate automation someone must build and maintain); VBA macros can fire alerts, but only when the workbook opens and they break in web/mobile Excel; or you duplicate dates into Outlook/Google Calendar, creating a second copy that drifts out of sync.

If dates carry real consequences, use a system whose whole job is watching them — spreadsheets are for calculating, not for waking you up.