Date and time notation in Spain
In Spain, the date order is day, month, year despite separators, Roman numerals for the month part and/or length for the year part. There is not a single fixed symbol for the separator, the most used being the stroke and the hyphen. Sometimes a dot is used, but it is rare. The hyphen tends to be clearly long when handwritten, and sometimes spaced.
Two-digit years are used for short mainly informally where no confusion arises, as in handwriting letters, notes and diaries. Official documents always use full four-digit years.
The suffixes for BCE and CE are "AC" (antes de Cristo, "before Christ") and "DC" (después de Cristo, "after Christ"), respectively. Sometimes "AD" for "Anno Domini" in Latin is used instead of "DC", but it is rare. Anyway, "DC" is omitted commonly for years past 200 CE.
Names of months and weekdays are written in lower case, thus being common nouns rather than proper nouns, except at start of a sentence, where they are capitalized following the Spanish rules. Exceptions are some highlighted Catholic dates, as Miércoles de Ceniza ("Ash Wednesday") or Domingo de Resurrección ("Resurrection Sunday"), which are always capitalized.
The week runs from Monday to Sunday. In Spanish, there exists a convention for single-letter day names: L means lunes (Monday), M means martes (Tuesday), X means miércoles (Wednesday), J means jueves (Thursday), V means viernes (Friday), S means sábado (Saturday) and D means domingo (Sunday). Basically, the initial letter of the weekday name, except for Wednesday which is an "X" to avoid confusion with Tuesday. Some public vehicles, as taxicabs, wear a letter meaning the driver's weekly day-off.
Official time is always given in 24-hour format. Traditional hour-minute separator is the dot (18.20), which still is in use in some environments as press, but today the colon is the preferred symbol (18:20). Leading zeroes for the hour part are optional (more common in automated output), but are mandatory for the minutes and the seconds parts, if the last appears (08:09:07). In speech, a time given in 24-hour format always is followed by the word horas: el concierto comenzará a las 15:30 "quince y treinta" horas ("the concert will start at 15:30").
Fractional seconds are given in decimal after a separator (dot, comma or apostrophe). For elapsed time, the notation with "h" for the hour counter, an apostrophe (') for the minutes and a double apostrophe (") for the seconds is also used, without trailing zeroes: 8h 7' 46" means "eight hours and seven minutes and forty-six seconds have elapsed". Sometimes an "m" and an "s" are used for the minutes and the seconds instead of the apostrophes: 8h 7m 46s.
In common spoken language, times are given in 12-hour clock, and those between 1 and 11 are assumed to be post meridiem, past noon, if not otherwise noted. After midnight, hours are labeled de la noche ("at night") until five on, which become de la madrugada ("at early") before sunrise and de la mañana ("at morning") after sunrise. When a post meridiem hour is labeled explicitly, it is de la tarde ("at afternoon") before sunset and de la noche ("at night") after sunset.
There are no traditional ante meridiem and post meridiem suffixes in Spanish; "AM" and "PM" are used when writing 12-hour format time, with any variation: "A.M./P.M.", "am/pm", "a.m./p.m.", "a/p ", etc. Ante meridiem suffix is often omitted.