The year is given as a complete number in Portuguese. So for example, 1999 is given as ’one thousand nine hundred and ninety nine’ rather than ’nineteen ninety nine’. The day of the year is given as the cardinal number rather than ordinal, (for example, they say the equivalent of ’day 4’ rather than ’the fourth’) – except for the first, which is normally ordinal (’primeiro’).
21st February 1763      21 de Fevereiro de 1763 (Dia vinte e um de fevereiro, de mil setecentos e sessenta e três)
19th July 1974             19 de Julho de 1974 (Dia dezanove de julho, de mil novecentos e setenta e quatro)
1st May 200                 21 de Maio de 2002 (Primeiro de maio, de dois mil e dois)
Going back further into history, you may need to refer to dates as ’AEC’ or ’EC’ – that is ’antes era comum’ (before our common era), or ’era comum’ (of our common era). You will probably also come across the less accurate but more common ’AC’ (antes [de] cristo) which means ’BC’ or ’Before Christ’, and ’DC’ (depois [de] cristo] – which means ’AD’ (anno domini – the year of our lord). Whereas in English we tend to just say the letters (eg. ’B.C.E.’), in Portuguese you have to say the full words (eg. ’antes era comum’). Also, the implied words ’de’ and ’nossa’ (’of’ and ’our’) are usually omitted, or sometimes contracted to ’da’.
English           Portuguese
537 BCE        537 AEC (Quinhentos e trinta e sete antes era comum)
33 CE            33 EC (Trinta e três era comum)
1336 BC       1336 AC (Mil trezentos e trinta e seis antes [de] cristo)
305 AD          305 DC (Trezentos e cinco depois [de] cristo)