Q Language Temporal Data - KDB+

What is Q Language Temporal Data?

The q language has many unique methods of representing and manipulating temporal information inclusive of times and dates.

Date

A date in kdb+ is internally saved because the integer quantity of days because our reference date is 01Jan2000. A date after this date is internally saved as a nice variety and a date before that is referenced as a bad number.

By default, a date is written within the layout “YYYY.MM.DD”

q)x:2015.01.22 / This is how we write 22nd Jan 2015 q)'int$x / Number of days since 2000.01.01 5500i q)'year$x / Extracting year from the date 2015i q)x.year / Another way of extracting year 2015i q)'mm$x / Extracting month from the date 1i q)x.mm / Another way of extracting month 1i q)'dd$x / Extracting day from the date 22i q)x.dd / Another way of extracting day 22i

Arithmetic and logical operations can be performed directly on dates.

q)x+1 / Add one day 2015.01.23 q)x-7 / Subtract 7 days 2015.01.15

The 1st of January 2000 fell on a Saturday. therefore any Saturday all through the history or within the future when divided by using 7, might yield a remainder of 0, Sunday gives 1, Monday yield 2.

Day mod 7 Saturday 0 Sunday 1 Monday 2 Tuesday 3 Wednesday 4 Thursday 5 Friday 6

Times

A time is internally saved because the integer number of milliseconds because the stroke of midnight. A time is written inside the format HH:MM:SS.MSS

q)tt1: 03:30:00.000 / tt1 store the time 03:30 AM q)tt1 03:30:00.000 q)'int$tt1 / Number of milliseconds in 3.5 hours 12600000i q)'hh$tt1 / Extract the hour component from time 3i q)tt1.hh 3i q)'mm$tt1 / Extract the minute component from time 30i q)tt1.mm 30i q)'ss$tt1 / Extract the second component from time 0i q)tt1.ss 0i

As in case of dates, arithmetic can be carried out at once on times.

Datetimes

A datetime is the aggregate of a date and a time, separated by using ‘T’ as inside the ISO standard layout. A datetime value stores the fractional day matter from midnight Jan 1, 2000.

q)dt:2012.12.20T04:54:59:000 / 04:54.59 AM on 20thDec2012 q)type dt -15h q)dt 2012.12.20T04:54:59.000 9 q)'float$dt 4737.205

The underlying fractional day count can be obtained by casting to float.