In a Facebook posting by David Palmer he posited that Dude Jr. (the child of the Dude in the film The Big Lebowski, whom I'm calling the Little Lebowski) would be in his/her early 20s. Surprised that I couldn't really find any reference online to anyone actually calculating the date, I sat down with my copy of the movie, and I posit that the Little Lebowski was born on 12 June 1992.
First, let's get rid of one misleading date — in the opening scene of the movie you can see the Dude writing a check which he dates "Sept 11, 1991". However, in an early scene the Dude's landlord says that "tomorrow's already the 10th", hinting that the Dude is late in paying rent. So I will argue that the landlord was mentioning the correct date, and that the Dude was either stoned and wrote the incorrect date on the check, or that he was post-dating the check.
During that same scene, the landlord mentions that he's going to be performing his dance quintet "on Tuesday night". Now, if "tomorrow's already the 10th", this is on 9 September 1991, which is a Monday. I will argue that the dance performance occurs on the Tuesday of the following week — 17 September 1991. If it was on the 10th, I think the landlord would have said "tomorrow", and, given the amount of stuff that happens in the movie, I feel it's more appropriately the next week. I don't think it's any time past the 17th (say, on the following Tuesday, the 24th), because at that point the landlord would have said "in two weeks" or given the date.
Here's what happens between the dance performance and the night of conception:
- Dance performance
- Larry Sellers' visit
- Walter apologizes, Jackie Treehorn's thugs show up
- Visit Jackie Treehorn
- Drug Sequence/"I Just Walked In To See What Condition My Condition Is In"
- Run-in with the Chief of Police of Malibu County
- Taxi scene
- Get home
Now, 1 and 2 happen the same night: they're at the performance, Walter comes in with the info about the kid, and says they'll pay him a visit after the performance. 3 -9 also happen the same day: as Walter phones in his apology right before the thugs show up and the rest happens in sequence. We also know that the conception happens on a Friday night — after conception and the Dude's relevation, he calls Walter, who reluctantly answers the phone because it is "erev Shabbas". Shabbas, the Jewish day of holy rest, happens from sunset on Friday until the apperance of three stars in the sky on Saturday night (so sayth Wikipedia). "Erev Shabbas" is the "eve of Shabbas", so this is a Friday night.
But what Friday? I argue it's the Friday immediately following our last known date, the 17th, which would be the 20th. Walter is apologizing for his actions the night of the 17th, asking if the Dude made it home and if he'll be at bowling. I think that Walter waiting more than a couple days is highly unlikely, especially since by asking if the Dude will be at bowling practice I presume he means they haven't practiced since the night of the 17th, and I think it's impossible they would go more than a few days without bowling practice.
With that in mind, I argue that the conception happened on 20 September 1991, and that, 38 weeks later (the standard length of a human pregnancy), the Little Lebowski was born on 12 June 1992.