In Mexico this is what you sing instead of Happy Birthday - at dawn if you love someone enough, with mariachis if you can afford them. The verses here are the anonymous ones the broadside presses of Mexico City were printing in the 1880s; a folklorist's wax cylinder caught a woman singing them in 1904, which is about as close to time travel as song provenance gets.
needs the culture note: traditionally you were congratulated on your saint's day - the feast day of the saint you were named after - and birthdays absorbed the custom later. The King David opener is the song's little joke of grandeur: these are the morning songs que cantaba el rey David, no less, brought to your window.
The last verse runs the verb - to dawn - through two forms in three lines: ya viene amaneciendo (dawn is coming on) and ya amaneció (day has broken). One verse, one verb, the whole difference between the gerund and the preterite.
One honesty note: most modern recordings, including the lovely one we link, add a famous "Despierta, mi bien" verse. It has a named 20th-century author and is still under copyright in Mexico, so we do not print it - the anonymous verses above are the song's oldest core.