The first question Earthers generally ask about another world is not, 'Does it have rain?' 'Does it have trees?' 'Does it have an atmosphere?' but 'Do they have Christmas there? And if so, is it called something different, like Hogswatch or Life Day?'
Barrayar, we know, celebrates Winterfair, which is tied to the Barrayaran seasonal cycle, and is sort of like Christmas but without being inconveniently Christian. But what about the rest of the Nexus?
Escobar: yes, they definitely celebrate Christmas. And Easter and Mardi Gras and lots of saints' days, such as St Lazarus, patron saint of cryo-revivals.
A number of people on Beta Colony believe in God, and some respect the teachings of Jesus, whether or not they believe that he was God. However, Christmas is not popular there, because, while there is nothing inherently unreasonable about a woman becoming a mother without having had sex with a man, the idea of someone being old enough to qualify for a parenting licence without having had sex with anyone at all is one that many Betans find disturbing.
Some planets have their own version of the Christmas story. As told on Athos, Jesus was God the Father's gift to the Virgin Marius, a virtuous boy who resisted the heteronormative pressures of his culture and stayed faithful to his partner Joseph, who was a loving Designated Alternate Parent to Jesus, as was Marius in time to Joseph's four sons. (The Athosian edition of the Bible removes references to Jesus having had sisters as well as brothers.)
In the Cetagandan version, Mary was a high-school student who designed Jesus as her eighth-grade biology project, giving him extra features like the ability to walk on water out of adolescent enthusiasm. And speaking of youthful enthusiasm, anyone who thinks Cetagandans have exquisite taste has not seen Christmas decorations made by Cetagandan schoolchildren. These range from the fairly simple in younger classes (such as spruce trees that bear apples) to the more elaborate by senior pupils (such as spruce trees that bear tiny reindeer calves on Christmas Eve, who mature rapidly, and sprout wings and fly away by Twelfth Night).
On Lairouba, celebration of Eid-al-Fitr and Eid-al-Adha depends on a tightbeamed message from Earth confirming a sighting of Earth's moon. However, only the ultra-orthodox bother using a gadget to confirm, at the time for each prayer of each day, where Earth (and therefore Mecca) currently is in relation to Lairouba, and therefore which way to face when praying.
On Kibou-Daini, the most important festival is Day of the Dead. Traditionally, this is the day for making payments to the cryocorporation housing your loved ones. For liberals, it is also a day to make donations to charities providing cryogenic freezing for those who are unable to afford to pay for it. For radicals, it is a day to pray that the souls of the dead will move on, and stop hogging all the resources and votes which rightfully belong to the living.