Navigation in The King’s Mirror, 1250s

Chapter 90

60-61

[...] one should not venture out on the ocean later than the time when October begins, because then the seas begin to become treacherous. The storms become more numerous and increase in strength the later in the fall and closer to winter it is. But the time when 16 October rolls around, the east winds become less joyous [...] and fierce [...]

63

Most seas, with the exception of the very largest, one can dare to set out on when April begins because when 16 March arrives, the days begin to become longer, the sun increases and the nights become shorter. [...]