Cinco de Mayo

Why, if the Titanic and it's 12,000 cases of Hellmann's were lost to an iceberg on 15 April, do Mexicans living in the United States mark it's demise 20 days later?
I have heard two explanations; 1, The speed of travel in 1912 meant that word of the disaster did not reach Mexico for three weeks, and they, in their grief, assumed it had happened the day before. By the time they learned the correct day, it had become a part of Mexican culture.
2, There is actually a 20 day period of mourning which ends on May fifth and they hold a celebration similar to the way splodydopes do with kerBLAMadon or what ever their period of fasting to Satan is called.