What the map shows, and how we know it is right.

What a star map shows

Your star map is the sky as seen from the place you enter, at the date and minute you enter, looking straight up. The centre of the circle is the zenith — the point directly above your head. The edge of the circle is the horizon. North is at the top unless you rotate it. Stars are drawn to their real brightness: the brighter the star, the larger the dot. Constellation lines and names can be switched on or off in the preview.

We draw stars down to magnitude 6.5, roughly what a good eye sees on a dark night. We do not draw planets, the Moon or satellites on star maps; the Moon has its own print. If the sky was cloudy that night, the map still shows what was behind the clouds.

How it is computed

• Place. The city or address you type is converted to coordinates with OpenStreetMap data. You can drag the pin to the exact spot — the church, the apartment, the bench.
• Time. The date and minute you enter are local time at that place. We use the IANA time-zone database to convert it to Universal Time, including the daylight-saving rules that applied on that date. A wedding at 16:00 in Vienna in June and one at 16:00 in December are two different skies, and both are placed correctly.
• Stars. Positions come from ESA’s Hipparcos catalogue (117,955 stars) and the Yale Bright Star Catalogue, both public domain. Catalogue positions are given for the year 2000; we precess them to your date, so a map for 1987 and a map for 2026 differ by the amount the Earth’s axis has drifted in between.
• Projection. The sky is projected onto the circle so that the zenith is at the centre and the horizon at the rim (a stereographic projection). It is the same view you get lying on your back.

City maps and where-we-met prints

City maps are drawn from OpenStreetMap, the free map of the world, rendered from our own data extracts in the styles you see in the preview. They show the map data as it stands on the day we render it, not the streets as they were on your chosen date — a bridge opened in 2019 is on a map for a 2015 anniversary. Every city-map print carries “© OpenStreetMap contributors · openstreetmap.org/copyright” in the footer, as the licence requires.

Where-we-met prints combine two or three places — the cities you came from and the place you met — with their coordinates. Coordinates are printed in degrees, minutes and seconds, to the precision of the pin you placed.

Moon phase

The moon-phase print is calculated for the chosen date at local noon at the chosen place: illuminated fraction, waxing or waning, and the angle of the terminator. It is a calculation, not one of twelve stock pictures, so a 37 % waxing crescent looks like a 37 % waxing crescent.

How we check

Before launch we compared ten star maps for known dates and places — from a 1969 Bratislava evening to a 2024 Lisbon sunrise — with Stellarium, the reference planetarium software, and we keep the log. Every change to the renderer is re-run against the same ten skies. If a delivered print ever differs from the preview you approved, or contains an error in our calculation, we reprint it free of charge — that is written into our terms.

Who we are, who prints

Zenitmap is a brand of Teamday s.r.o., a two-person company in Bratislava, Slovakia. We wrote the renderer and we answer the emails. The prints themselves are produced by Gelato and Printful in their EU facilities — Germany, the Netherlands, Poland, Spain, Latvia, depending on where you live — on matte 200 g paper, stretched canvas or in black and oak wooden frames, and shipped directly to you. The producer’s name and address are shown on every product page, as EU product-safety rules require.

Questions about a map, a date, a place we could not find? Write to shop@teamday.ai or use the contact page. We reply within one working day.