What happened to flags on 17 May
3 flags in the atlas carry this date. The sentence under each one is where that is written down, in its own article.
- France 1853
Under Napoleon I, the proportions were changed to make the stripes' width equal, but by a regulation dated 17 May 1853, the navy went back to using the 30:33:37 proportions, which it now continues to use, as the flapping of the flag makes portions farther from the halyard seem smaller.
From Flag of France on Wikipedia, as it read on 2026-08-29
- El Salvador 1912
On 17 May 1912, the Legislative Assembly adopted the blue-white-blue triband as the national flag of El Salvador.
From Flag of El Salvador on Wikipedia, as it read on 2026-08-26
- United States Virgin Islands 1921
The flag of the United States Virgin Islands was adopted on May 17, 1921.
From Flag of the United States Virgin Islands on Wikipedia, as it read on 2026-08-26
How a day gets onto this site
A flag is here because a sentence in its own English Wikipedia article puts it on this date, and that sentence is printed above. Nothing was worked out from a year, and nothing was written for the occasion. Every sentence names the article it came from and the version of that article it was read in, so you can go and check it.
The calendar is still short rather than full. A third of the year has no page here, because a flag only gets a day when a sentence in its article puts something on one, and plenty of articles never do. Nothing is invented to fill the gap.