COB stands for "close of business". Refers to the time when companies close at the end of the business day. Typically occurs at 5 pm local time in the United States
16:30 can be expressed as 4:30 PM in regular time. Military time uses 24-hour format, starting at midnight. Military hours are numbered from 00 to 23
Half past means 30 minutes after an hour. Quarter past means 15 minutes after an hour. Digital clocks use 24-hour system with AM and PM
There is no strict agreement on "afternoon" and "evening" meanings. "Afternoon" generally refers to 12-6pm time range. "Evening" traditionally starts when sun goes down
Time zones are commonly represented by alphabetic abbreviations like EST and WST. These abbreviations are not part of ISO 8601 standard. "CST" can mean China, Cuba, or North American Central Standard Time. These abbreviations predate ISO 8601 and internet era. In earlier times, they were sufficient for national contexts
Singapore adopted Malayan Time (GMT+07:30) in 1941. During Japanese occupation, adopted Tokyo Standard Time (GMT+09:00) in 1942. Singapore reverted to pre-war time zone after WWII