The FromDate command converts a date in year, month, day, hour, minute, second format to number of seconds since January 1, 1900.

$\mathrm{with}\left(\mathrm{MmaTranslator}\left[\mathrm{Mma}\right]\right)\:$

$\mathrm{FromDate}\left(\left[2004\,1\,1\,0\,0\,0\right]\right)$

$3.281920223\times {10}^9⟦s⟧$

$\mathrm{with}\left(\mathrm{MmaTranslator}\right)\:$

$\mathrm{FromMma}\left(\mathrm{`FromDate[\{2004,\; 1,\; 1,\; 0,\; 0,\; 0\}]`}\,\mathrm{evaluate}\right)$

$3.281920223\times {10}^9⟦s⟧$