In De ratione temporum (On the reckoning of time), chapter 15, the Venerable Bede lists the English months:
In olden time the English people — for it did not seem fitting to me that I should speak of other nations’ observance of the year and yet be silent about my own nation’s — calculated their months according to the course of the moon. Hence, after the manner of the Greeks and the Romans, [the months] take their name from the moon, for the moon is called mona and the month monath.
The first month, which the Latins call January, is Giuli; February is called Solmonath; March, Hrethmonath; April, Eosturmonath; May, Thrimilchi; June, Litha; July, also Litha; August, Weodmonath; September, Halegmonath; October, Winterfilleth; November, Blodmonath; December, Giuli, the same name by which January is called. They began the year on the 8th kalends of January [25 Dec.], when we celebrate the birth of the Lord. That very night, which we hold so sacred, they used to call by the heathen word Modranecht, that is, ‘mother’s night’, because (we suspect) of the ceremonies they enacted all that night.
The months of Giuli derive their name from the day when the sun turns back [and begins] to increase, because one of [these months] precedes [this day], and the other follows. … 
‘Giuli’ is Yule, I believe. Note how it is a two-month month.
- Bede, The reckoning of time, translated … by Faith Wallis. Liverpool, 2004, p.53-4↩