Everyday & Conversions
Expiration Date Calculator
Work out an expiry or best-before date from a production date and a shelf life, and see how many days of life are left.
Your inputs
Change any value to update the result instantly.
Expiry date
Tuesday, 30 June 2026
Days of life left
90 days
Shelf life used
50 %
Status
Still within shelf life
This is date arithmetic only. Always follow the manufacturer's own storage instructions and discard anything that looks or smells wrong.
What this calculator does
Adds a stated shelf life to a production or opening date.
What your result means
The expiry date and how many days of stated shelf life remain.
Formula and working
Expiry date = production date + shelf life; days left = expiry date − today
- 1
Collect the inputs
Production or opening date = 2026-01-01; Shelf life = 180 days; Check against this date = 2026-04-01
- 2
Apply the formula
Expiry date = production date + shelf life; days left = expiry date − today
- 3
Result
Expiry date = Tuesday, 30 June 2026
Frequently asked questions
Symbols and assumptions
- S
- Shelf life in days
- D₁
- Start or birth date on the Gregorian calendar
- D₂
- Reference or end date
- Δd
- Whole days between the two dates
- • Proleptic Gregorian calendar with real month lengths (28, 29, 30 or 31 days).
- • Leap years follow the rule: divisible by 400, or by 4 but not by 100.
- • Dates are handled in UTC so a device time zone cannot shift a calendar day.
- • Shelf life is the figure you enter, taken in whole days.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Dates before 15 October 1582 used the Julian calendar in most of Europe and are outside the intended range.
- • Clock-time results ignore daylight-saving transitions unless the tool asks you to set them.
- • Real shelf life depends on storage conditions. Always follow the manufacturer's instructions; this is not a food-safety ruling.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
Report a mistake or request an improvement
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