Time conversion deals with "duration" rather than "moment". Values such as 30 seconds, 90 minutes, 72 hours, 3 weeks, and 6 months all represent how long they last, so they can be converted linearly to each other using a fixed ratio. On the contrary, date and time such as a certain year, a certain day, a certain month, a certain time and a certain minute are not the objects of this page, because they will be affected by time zone, daylight saving time, leap year and specific number of days in the month.
In short delay scenarios, ns, μs, ms, and s are the four most common groups of units. Program performance, hardware responsiveness, database latency, animation frames, and network latency often switch back and forth between these units. After unifying the unit, the same monitoring charts, logs and documents are easier to compare horizontally, and misreadings can also be reduced by orders of magnitude.
In daily and operational scenarios, minutes, hours, days, and weeks are the most practical expression levels. For example, a 45-minute meeting, a 12-hour shift, a 3-day delivery, and a 2-week sprint. When making reports, it is often necessary to unify time fields from different sources into the same magnitude, so that summation, averaging and sorting will be more stable.
The month and year in this page adopt fixed caliber: 1 month = 30 days, 1 year = 365 days. This writing method is suitable for unifying estimates, reports and budget cycles, but it is not suitable for calculating due dates, salary settlement dates or days of leave on the real calendar. As long as the scene involves a specific date, calendar logic should be used instead.
Time and frequency often go together. Time is how long a cycle is, and frequency is how many times it occurs per unit time. When doing cycle, sampling, vibration or refresh rate analysis, it is usually the clearest and least error-prone approach to unify the time into seconds before deriving subsequent formulas.
