Still goooogling it Carlos . Its hard to find a definative answer eh .
A decade is a span of ten years. The first year of the Christian era was 1AD and it was preceeded by 1BC. The first decade of the Christian era was therefore 1 to 10AD, the second 11 to 20AD, the third 21 to 30AD and so forth. The first millenium of the Christian era was 1 to 1000AD, followed by the second 1001 to 2000AD and our current millenium started on 01.01.2001.