Unlike other Meridians International Date Line is drawn zigzag in order to

The International Date Line (IDL) is an imaginary line of demarcation that separates two consecutive calendar dates [1][t1]. Unlike standard meridians which are straight lines from pole to pole, the IDL is drawn in a zigzag manner to avoid splitting a single country or island group into two different calendar days [c2][t4]. If the line followed the 180° meridian strictly, it would cause significant administrative and social confusion by forcing different parts of the same nation to operate on different dates [c2][t9]. For instance, it deviates at the Bering Strait to keep eastern Russia on a single date and curves around island nations like Kiribati and Tonga to ensure they share the same calendar day [c1][t8]. This practical adjustment allows political and geographical entities to maintain a unified time and date system across their territories [c5][t3].

Sources

1. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > The International Date Line > p. 14