For grins, remove the AC control panel and spray contact cleaner on both halves of the connector/s.

If you can identify the fuse that serves clock memory, replace it for good measure.

Sixto
‘04 LE FWD 228K miles

 

Loose battery terminals or corrosion. In some cases, corrosion can work its way back into the wire insulation. I see online the suggestion of turning the key to on, check the time, if it's correct, start the car, if it resets to 1:00, it's the battery or cables. If it's not the battery/cables, you're probably looking at a partial short in one of the climate control things (where the clock gets its power). Radio presets get power from a different source.

 

Clock is with climate control, all original. Battery 1 year old, alternator replaced 1 year ago, terminals tight, radio presets do not reset when it happens

 

Is this the basic clock under the AC vents or is it part of the upgrade stereo? Guessing upgrade if limited.

Does the van have aftermarket stereo or remote start or such features?

Sixto
‘04 LE FWD 228K miles