int doomsday_gregorian ( int y, int m, int d );
int i4_max ( int i1, int i2 );
int i4_min ( int i1, int i2 );
int i4_modp ( int i, int j );
int i4_wrap ( int ival, int ilo, int ihi );
void timestamp ( );
string weekday_to_name_common ( int w );
void weekday_values ( int &n_data, int &y, int &m, int &d, int &w );
bool year_is_leap_gregorian ( int y );