Nature Journal & Phenology Tracker
Record first bloom, first swallow and first frost year after year, compared by day-of-year rather than by date — stored in your browser.
Record the same events every year. A single year of dates is a diary; several years is a record of what the seasons are doing where you live.
Year on year
All records
| Event | Date | Day of year |
|---|
Why day-of-year, not the date
Comparing "12 March" with "5 April" across years means doing arithmetic in your head, and it goes wrong across a leap year. Converting each record to a day number — 1 to 365, or 366 — makes the comparison immediate and correct, which is exactly how phenology networks store their data.
Phenology is one of the few areas of science where a private notebook still contributes something real. Long personal records — the Marsham family kept one in Norfolk for nearly two centuries — are the reason we can say anything at all about how first-flowering and first-arrival dates have moved, because no institution was recording them.
Two things make a record worth keeping. Consistency — the same events, the same place, judged the same way each year — and honesty about the misses, because a year you were away and did not see the first swallow is not a year the swallow was late. Note the gap rather than guessing.
How to use
- Record each event as you observe it.
- Note the date and, ideally, the location.
- Compare across years by day-of-year.
- Keep observing the same things in the same place.
Frequently asked questions
What is phenology?
The study of recurring biological events and their timing — first flowering, leaf-out, bird arrival, insect emergence, first frost. It is among the oldest forms of systematic natural observation, and one of the few where an amateur record has genuine scientific value.
Why compare by day-of-year rather than by date?
Because it makes years directly comparable as numbers and handles leap years without special cases. Saying an event fell on day 96 rather than the 6th of April lets you compute a mean, a trend and a departure from normal without any calendar arithmetic.
Are these records scientifically useful?
Some of the most valuable long-term climate records are exactly this. The cherry blossom records in Kyoto extend back over a thousand years, and observations from naturalists such as Thoreau have been used in modern research on shifting seasons. A consistent personal record genuinely contributes.
How many years before a trend means anything?
More than you would like — a decade at minimum, and considerably more for confidence. Year-to-year variation in biological timing is large, so a single early spring says nothing. The value of these records comes from persistence rather than precision.
What should I record?
Things you can identify reliably and observe in the same place each year. First flowering of a specific plant you can see, first appearance of a species you know well, and first and last frost are all good. Consistency of what and where matters far more than the number of events.
Where is my journal stored?
In your browser on this device, with nothing uploaded. That also means it does not sync and will be lost if you clear browsing data — so a record intended to run for decades should be exported regularly and kept somewhere durable.
🔒 This tool runs entirely in your browser. Nothing you enter is uploaded, logged, or stored.