Treason is merely a question of dates.

Charles Maurice, Prince de Talleyrand-Périgord (1754-1838) French statesman
Comment to Tsar Alexander (1815)
    (Source)

Variant: "Treason is merely a matter of dates."

Both versions of the line are quoted in different biographies of Talleyrand, apparently derived from a passage in his Memoirs (ed. Albert de Broglie, tr. De Beaufort (1891)). He relates while at the Congress of Vienna (1814-15), Tsar Alexander referred to Saxony as "Those who betrayed the cause of Europe" for joining with Napoleon, to which Talleyrand replied (mindful that Alexander had at times been allied with Napoleon), "Sire, that is a question of dates."

In the movie Die Hard 2 (1990), the quote is misattributed to Cardinal Richelieu in Alexandre Dumas, The Three Musketeers (1844). Variants on the line actually have been used in movie editions of Dumas' The Count of Monte Cristo (but not in the actual book).