Weekend is Just Another End
While weekend may be a time expression, it is relatively new to the language. Until Saturday became only a half day of work in England’s industrial North, there was no need — a worker’s free time was Sunday, and that was it:
In Staffordshire, if a person leaves home at the end of his week’s work on the Saturday afternoon to spend the evening of Saturday and the following Sunday with friends at a distance, he is said to be spending his week-end at So-and-so. — Notes and Queries, Fifth series, vol. 12, July–Dec. 1879.
As a compound noun of recent provenance, then, it shouldn’t be surprising that weekend behaves in some syntactical contexts as its final element, i.e., when and where it requires the definite article:
In British English:
Great business plans begin at the end. — Summary of David Lavinsky, Start at the End, 2012, 2014.
If I'm offered a job on Friday, we can make plans at the weekend. — Ruth Dudley Edwards, The English School of Murder, 2000.
In American English:
And like their neighbors, they had a long gray wooden pier with a small seating area with a tin roof on the end. — Fannie Flagg, The All-Girl Filling Station's Last Reunion, 2013,10.
The seed for Disneyland was planted when Walt would take his daughters, Sharon and Diane, to an amusement park or to Santa Monica Pier on the weekend. — Keith Abraham, It Starts with Passion: Do What You Love and Love What You Do, 2019.
In all flavors of English with until:
As they fight for their lives and race for their freedom, they'll discover that what they truly need in order to survive until the end. — Tracy Ward, Until the End, 2013.
Headline: Belgian heatwave: Thalys train service disrupted until the weekend. — Brussels Times, 26 July 2019.
The background music during the end is Mind Over Matter by Dottie from the Pee Wee movie. I'm too lazy to look up her name. — World of Prank Calls, 24 Mar. 2019.
The music during the weekend was spectacular. — Event Review: Rose City Blues 2013, Blues Dance World, 21 Nov. 2013.
I'm currently 2nd... The end will be exciting! — Pictame.com, 6 April 2019.
So while the weekend will be exciting for the players, it can also be an exciting glimpse into the future for the organization. — Prospect Camp Weekend Has Arrived – Moose Jaw Warriors, 23 May, 2013.
If the world should stop revolving, spinning slowly down to die,
I’d spend the end with you. — David Gates, “If,” 1971.
She wasn’t content to spend the weekend with the most eligible hunk in the western hemisphere. — Rita Clay Estrada, One Wild Weekend, 1999, 98.
Adverbial, Attributive Use
When used adverbially with a demonstrative or temporals like next or last, weekend behaves like a month:
Just as you can’t say
*We’re planning a trip to Iceland *June (this/for/in June)
you can’t say
We’re planning a trip to the countryside *weekend.
And you’re back to the prepositions above.
Except today, yesterday and tomorrow, which require a possessive (tomorrow’s flight), and those that take a -long compound (day, month, year) weekend can be used attributively as other time expressions:
We’re planning a Sunday/morning/July/weekend trip.