How to read a Maxi-Cosi week and year code on an ISOFIX base

What does a four-digit code such as 5010 mean?

WWYY — week of the year, then the two-digit year. 50 is the week. 10 is 2010. Maxi-Cosi UK customer care, in a reply quoted on BabyCentre, read a base stamp of 5010 as "week 50 of the year 2010".

US Maxi-Cosi / Dorel consumer-care pages often show MM/DD/YYYY. That is a different label family. A UK FamilyFix-style code is not a US month and day.

Where is the week-and-year code on the base?

1. 1
   Take the carrier off and tip the base The mark is on the base, not on the fabric of the infant carrier.
2. 2
   Find the underside sticker Which? describes Maxi-Cosi FamilyFix-style bases as carrying the date and reference underneath. On older units parents have also reported a four-digit number at the bottom of a barcode panel.
3. 3
   Copy every field, not just the four digits Model or item reference, serial, and the date code. Official notices name those fields. This page stops at reading the date. For a batch or recall check, use the maker's current notice and the GOV.UK Product Safety list — not a how-to on this page.
4. 4
   Photograph in daylight Orange or white stickers fade. A second photo of the whole underside shows you have not cropped a fifth digit.

Does decoding 5010 tell me how many years I can use the base?

No. Decoding gives you a manufacture week. How many years Maxi-Cosi wants that base used is a different sentence, and it has changed between models. A 2017 Maxi-Cosi UK care email spoke of intensive use of about 10 years and, on that 5010 base, named week 50 of 2020 as the replacement point they advised. The official CabrioFix i-Size base manual later says that base is developed for intensive use of about 6 years.

Do not invent a current Maxi-Cosi year and add it to 5010. Open the PDF for your base. Does the base expire separately from the carrier?

RoSPA notes that UK seats are not marked with an expiry date. Child Car Seats still wants the manufacturer's own years-of-use advice. GOV.UK sets the legal E-mark and when a child must use a child seat — not a WWYY decoder.

What if my Maxi-Cosi label is not four digits?

Newer bases may print a full day, month and year next to "Date" or "Manufactured". Read that as a calendar date. Some shells also carry a moulded clock stamp. If two marks disagree, photograph both and ask Maxi-Cosi UK which one they use for that model.

A week number must be 01–53. If your first pair is 54 or higher, you are not looking at WWYY — you may be on a model code, a line code or a US-style date. Stop and compare the whole sticker with the current manual's diagram.

In shortWWYY = week then year. 5010 = week 50 of 2010. Look under the base, copy the reference as well as the code, and do not treat the digits as a US month/day. Years of use and batch notices are separate jobs for the current model PDF and the official lists.