Strefa czasowa +5 and other 65,000 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
It is a combination of two overlayed objects. The background object is a generic map-like object that has zig-zag top and bottom edges and dots scattered on it. The foreground object is a circle in the lower-right of the map that has a large "+5" text in it.