Paco Rabanne, Jean Paul Gaultier and Zara Batch Codes (Puig)

Paco Rabanne (now styled Rabanne), Jean Paul Gaultier, Carolina Herrera, Nina Ricci and Zara's fragrance line have no obvious connection — a Spanish fashion house, a French couturier, a Venezuelan-American designer, a Parisian maison and a high-street retailer. They share a manufacturer: Puig, the Barcelona family group that owns or licenses all of them.

That is why an Invictus and a Zara eau de toilette carry the same style of code. As everywhere in fragrance, the format follows the factory rather than the logo.

Puig does not run a proprietary cipher. It prints the production date inside the batch code, most often as a year digit followed by the day of the year — 4135 is the 135th day of a year ending in 4, that is 14 May 2024.

Some lines print a longer form instead: five digits (two year digits and the day) or a six-digit packed calendar date in YYMMDD order. Our reader tries each shape and reports which interpretation it used.

• Four digits: the first is the year's last digit, the remaining three are the day of the year. Divide the day by about 30.4 for the month.
• Five digits: the first two are the year, the last three the day.
• Six digits: read as year, month, day.
• If two readings both produce a valid date, prefer the one that makes sense for the bottle — a date before the fragrance launched is telling you the reading is wrong.

On the base of the outer box, and on the underside of the bottle — printed on the base sticker or, on the heavier Paco Rabanne bottles, stamped into the glass or the metal. Zara's fragrance boxes carry it on the bottom flap.

The box code and the bottle code should agree. They are applied minutes apart on the same line, and a mismatch is a sign the box and the bottle were paired somewhere other than the factory.

The four-digit form carries only one digit of year, so it repeats every decade. The decoder assumes the most recent reading; a bottle that clearly belongs to an older era may be ten years older than the decode suggests.

And the code is a date, not a certificate. Paco Rabanne and Jean Paul Gaultier are among the most counterfeited fragrances in Europe, and a counterfeiter who copies a genuine code produces a code that decodes perfectly. Use the date as one signal, alongside the weight of the glass, the quality of the atomiser spray and the small print on the box.