"Lunch Break," a comic strip, debuted in Star Wars Tales 16 and later found its way into the compilation Star Wars Tales Volume 4.
A stormtrooper named Kjazhed-Uhl is having lunch with his stormtrooper buddy, Bob. During their meal, Bob produces Darth Vader's personal diary, which they proceed to examine. Inside, they discover a collection of disconnected thoughts, recollections, and sketches. They then stumble upon a more recent entry detailing how the stormtroopers overlooked his birthday, leading to a day of solitude, tears, and excessive drinking until he reached a state of overwhelming emotion and unconsciousness.
Following this, Bob and Kjazhed-Uhl are present at a briefing. As they are exiting, one of the two pals offers Vader a belated birthday greeting. In response, Vader appears to express a subtle smile, though concealed by his mask.