How to use the allergy prep start date calculator
Enter a reference date, the date you expect symptoms to start and the lead time you have chosen. The page counts back to the date your preparation should begin, and also counts the days from the reference date to both the prep start and the expected onset. One week converts to seven days, and leap years and month ends fall out of the date arithmetic.
Figures this page does not use
Regional pollen counts and pollen season dates could not be confirmed in an authoritative source, so the page does not pick an onset date for you. The date last year's symptoms began, or a date your clinician gave you, works better. There is no published figure for how long a lead time should be either, so that is your input as well.
This page only counts days. It does not classify how long symptoms last or how severe they are, and it does not decide which medication to start or when. Duration and severity of allergic rhinitis are handled by the ARIA classification, and the trigger allergen can only be identified by testing. Decide the timing of any medication with a clinician (as of October 2026).
Frequently Asked Questions
Use the date symptoms first appeared last year. Regional pollen season figures could not be confirmed in an authoritative source, so this page will not pick a date for you.
No published figure is offered. Use the interval your clinician suggested or what worked last year. With the unit set to weeks, one week converts to seven days.
That means your reference date is later than the prep start date, and the page shows how many days ago it was. The page only counts dates, so discuss what to do next with a clinician.