====== Useful 'date' Commands ======

**Step the system time** by a specific amount (run as **''root''**):

<codedoc code>
date -s "+1 second"      # adjust the system time by +1 second
date -s "-0.01 second"   # adjust the system time by -10 milliseconds
</codedoc>

\\
Display the **current** UTC date as **seconds since epoch**:
<codedoc code>
date -u +%s
1594828693  # = 0x0x5F0F2795
</codedoc>

\\
Display a **specific** UTC date or time as **seconds since epoch**:
<codedoc code>
date -u -d "2020-07-15" +%s
1594771200  # = 0x5F0E4700
</codedoc>

<codedoc code>
date -u -d "17:30:00" +%s
1594834200  # = 0x0x5F0F3D18
</codedoc>

\\
Display the **human readable date and time** for specific seconds since epoch:
<codedoc code>
date -u -d @1483228800
Sun Jan  1 00:00:00 UTC 2017
</codedoc>

\\
Display the **human readable date and time** for the last second before the signed 32 bit Unix time_t rolls over,
and for the next second thereafter.
Use the ''printf'' command to determine the associated decimal number of seconds to be passed to the ''date'' command.
<codedoc code>
# last second before rollover (same on 32 and 64 bit system)
date -u -d @`printf "%i" 0x7FFFFFFF` +'%F %T'
2038-01-19 03:14:07

# first second after the rollover (on 64 bit system)
date -u -d @`printf "%i" 0x80000000` +'%F %T'
2038-01-19 03:14:08

# first second after the rollover (on 32 bit system)
date -u -d @`printf "%i" 0x80000000` +'%F %T'
date: ~~codedoc: <b>invalid date `@2147483648'</b>~~
</codedoc>

----

 --- //Martin Burnicki [[martin.burnicki@burnicki.net]] last updated 2020-07-15//