943
Or we could do metric time
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That's a common misconception. For the Romans, the year used to start with March and only have ten months. January and February weren't even named, it was just the time between harvest and the new year. Several calendar changes followed over the centuries. Adding two months (January and February). Moving the new year to January, which made September-December no longer 7-10. Adding random one-off months to realign with the seasons. And a couple different tries at leap days, among other things.
This gives a quick overview.
Edit 2: To clarify, the above changes were all made by the Romans, they only started with a ten month calendar.
Edit: The fifth and sixth months were originally named Quintilis and Sextilis before they were changed to July and August.
The Romans had twelve months and they even named January and February, it's usually attributed to Numa Pompilius, second king of Rome sometime during his reign (715–672 BC) of the Roman Kingdom.
All covered in the link. The addition of January and February and later moving the new year from March to January is the reason Sept-Dec are no longer the seventh-tenth months. Not July and August, which were renamings, not additions.
Edit: I suppose my first comment should have specified early Romans. The way I wrote it could be read as all those changes happening after the Romans.