date command --> used to display or set the date and time of the system; formatted output
【Display time】
date # display year, month, day, week, CST
date '+%c' # display year, month, day, hour, minute and second
date -I # Display year-month-day 2017-02-17
date '+%D' # show the full time
date '+%x' # Display numeric date, year with two digits representing May 12, 2010
date '+%T' # display the date, the year is represented by four digits 14:09:31
date '+%X' # display 24 hour format 14:09:39
date '+%T%n%D' # Skip the line after displaying the time, and then display the current date
date '+%B %d' # display month and day
date -u # Display date and time in UTC
date -d 'dec 30 -2 weeks' # show the time two weeks ago compared to December 30
【Add and subtract operations】
date +%Y%m%d # Display the year, month and day of the previous day
date -d "+1 day" +%Y%m%d # Display the date of the previous day
date -d "-1 day" +%Y%m%d # Display the date of the next day
date -d "-1 month" +%Y%m%d # Display the date of the previous month
date -d "+1 month" +%Y%m%d # Display the date of the next month
date -d "-1 year" +%Y%m%d # Display the date of the previous year
date -d "+1 year" +%Y%m%d # display the date of the next year
date -d '30 days ago' # Display the time 30 days ago
date -d next-month +%Y%m # Display the next month time
12 hours later 2 minutes ago
