With the equipment development timelines we know about, what is the soonest date a manned lunar landing could take place?
We could conceivably have a manned mission anytime (given a few years heads up) if it wasn't for the lack of interest in going to the Moon. Lack of Public Interest in the Moon.
The Apollo program gives a baseline: from May 1961 (Kennedy's speech) to July 1969 (Apollo 11 landing), so 8 years. That included inventing a lot of the technology and procedures needed, cranking up the industrial base, and the most expensive peacetime development program to date.
Design of the LEM started in 1963 (after 2 years of deciding on what configuration to use), LM-1 flew in 1968.
These days, it might be quicker than that, given that we already have rockets capable of reaching the moon, although you'd have to use 2-3 launches and Earth Orbit Rendezvous. You would need to design the CSM and LM, plus probably an upper stage. How much time that takes depends on how much time pressure you're under (lots of overtime during the Space Race), and how big your budget is. It's hard to imagine it taking less than the 5 years it took to get the LM ready.
https://en.m.wikipedia.org/wiki/List_of_missions_to_the_Moon Russia and Japan have current plans for a manned mission in 2030, China in 2036. The US and SpaceX have a manned mission planned for lunar orbit in 2023.