Unlike other anime, Kafka Asagiri and Sango Harukawa’s manga, Bungo Stray Dogs does not really specify what specific time or era it took place in. However, many speculate that the manga actually follows the era of the actual year it was published, meaning around the 2000s-2010s (the first volume of the manga was published in 2012).
Although this is without concrete evidence, the reason why fans deduced this is that the technology displayed in the anime and even the character design and fashion adheres greatly to the trends from the early 2000s to the late 2010s.

The reason for the big gap is the time period the manga was set in and the overall mood or feeling of the anime and manga is different. As mentioned earlier, it is theorized by some that the anime may have been set in the 2010s, but that’s the actual time period and not the mood. The anime’s mood or feeling greatly depicts the era during the late 90s or early 2000s.
This is somewhat an interesting thought especially if we look closer into one of the scenes in the hit manga and anime series. If you can recall, there was a specific bar that Dazai’s old friends, Oda and Ango used to frequent.

During this particular episode, we can clearly see the whole 90s mood of the anime bloom. The place looked like an old shack, no one else was inside but them, and there were drinks. When they decided to take their first and last picture together, we see that the camera Ango used to take the picture was an old camera, probably one you’d find in a classic 90s or even 80s film.
Much later in the season, we find out that this scene was actually not too long from the present. Dazai left the port mafia after Oda’s death, he joined the ADA when he was 20, and his current age in the manga is 23. So if the events were to be added up, the manga’s time period should be in between the 2000s – 2010s.
The fourth season of the Bungo Stray Dogs anime is now streaming on Crunchyroll in both Dub and Sub!
Read More: What is Bungo Stray Dogs Season 4 About?