Because of the international nature of sea travel where vessels traverse large distances, especially in east/west directions, time is a very important aspect of the mariner’s life. For convenience sake a “24 hour clock” is used. This means that by merely looking at the time will indicate whether forenoon or afternoon is referred to, ie 0001 to 1159 will indicate forenoon and 1200 to 2359 will indicate afternoon. The suffixes AM and PM are not used. In this section we will be referring to what one could call categories of time, ie Universal Time or Greenwich Mean Time, Local Mean Time, Zone Time and Standard Time. Each has a specific application as we shall see.