The International Standard lays down rules for signs and reference directions and reference polarities for electric currents and voltages in electric networks, as well as for the corresponding quantities in magnetic circuits. In clauses 3 to 9, the time dependence is arbitrary. Clause 10 details the rules and recommendations for complex notation.
DS/EN 60375:2004 history
2004DS/EN 60375:2004 Conventions concerning electric and magnetic circuits