Issues of peace have always been important for historical science. However, in recent years, international historiography has started to pay attention to the symbolism and socio-cultural design of peace congresses. The symbolic power of “special days” – whether it is a Christian holiday or an event of exceptional significance – allowed people of early Modernity to express their attitude to reality and power. An analysis of the choice of dates for concluding peace by adversarial states within the Westphalian system demonstrates three consistent options. The first is signing a peace treaty on a Saturday, Sunday, or a Christian holiday. The most striking example of this option is the signing of the Peace of Westphalia itself (the treaties of Münster and Osnabrück on October 24, 1648), on a Saturday – the day before the second Sunday after Trinity. The second option involves a reference to an important event in the past. For example, the Peace in Passarowitz between the Holy Roman Empire and Porta (1718) and the Treaty of Küçük Kaynarca between Russia and Turkey (1774) were signed on the same date – July 21, the date when Istanbul and Peter the Great signed the Treaty of the Pruth in 1711. Since the age of the Enlightenment, when the “Right to Peace” began to compete with the “Right to War” in political theories, the date of peace could be directly determined by the end of negotiations. Sometimes the conclusion of peace became a Christian holiday. Peter the Great decided to consecrate the day of the conclusion of the Nystad Peace Treaty by transferring the relics of the Holy Grand Duke Alexander Nevsky from Vladimir to the new Russian capital – St. Petersburg. The conclusion of peace in this case was used as a tool of social constructivism, implemented through modelling. The political idea was symbolically grounded in significant historical or religious dates. Combining the historical precedent, the Christian holiday and the end of the war emphasized the sacred nature of Peace as the highest social value.