The overly eager train reportedly pulled out of the Minami-Nagareyama station at 9:44:20 a.m. on November 14.
According to an article this month on the Gendai Business website, Tsukuba Express, which carries 130 million passengers a year, markets its "safety and high speed".
Japanese train services are famed for their punctuality, with significant delays relatively uncommon.
Looks like we all need to move to Japan - they take their train schedule very seriously.
The 20-second gaffe may not sound like a big deal, but the Japanese train system is world-famous for its precision and efficiency.More news: No. 4 Louisville gets bye in NCAA men's soccer tournament
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Management on the Tsukuba Express line between Tokyo and the city of Tsukuba say they "sincerely apologise for the inconvenience" caused.
At first, I sort of agreed with him. It was supposed to leave one minute later, at 9:44:40 - but instead, it left at 9:44:20.
"Because Japanese trains are usually so punctual, some people plan their rail commutes so that they arrive at the platform just as the cars are pulling up", Baseel said.
One amused reader said: "This train company's apology for a 20-second-early departure is one of the best things about Japan".
So yeah, if someone at Metropolitan Intercity Railway Company got reamed out by his boss for a 20-second screw-up, I feel for him, since I don't think it's worth getting that bent out of shape about.
While issuing the mea culpa, the company noted that it actually had not received any customer complaints.