axis index or column in dataframe the to_datetime method parses many different kinds of date representations standard date formats like iso can be parsed very quickly in [ ]datestrs out[ ][''''in [ ]pd to_datetime(datestrsout[ ] : : : : length freqnonetimezonenone it also handles values that should be considered missing (noneempty stringetc )in [ ]idx pd to_datetime(datestrs [none]in [ ]idx out[ ] : : natlength freqnonetimezonenone in [ ]idx[ out[ ]nat in [ ]pd isnull(idxout[ ]array([falsefalsetrue]dtype=boolnat (not timeis pandas' na value for timestamp data dateutil parser is usefulbut not perfect tool notablyit will recognize some strings as dates that you might prefer that it didn'tlike ' will be parsed as the year with today' calendar date table - datetime format specification (iso compatibletype description % -digit year % -digit year % -digit month [ % -digit day [ % hour ( -hour clock[ % hour ( -hour clock[ % -digit minute [ % second [ (seconds account for leap seconds% weekday as integer [ (sunday) time series www it-ebooks info