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.