# [APL (Dyalog Unicode)], 51 bytes

<!-- language-all: lang-apl -->

Full program body.

    s←⎕AI
    1↓∊':'@1∘⍕¨100+3↑0 60 60 1E3⊤3⊃⎕AI-s
    ⎕DL 1
    →2

[Try it online!][TIO-jbnj0ecc] (Press Ctrl+Enter to start, and again to stop.)

`⎕AI` **A**ccount **I**nformation (user ID, compute time, connect time, keying time)

`s←` assign to `s` (for **s**tart time)  
`⎕AI-s` subtract `s` from `⎕AI`

`3⊃` pick the third element (connect time in milliseconds)  
`0 60 60 1E3⊤` convert to this mixed-radix  
`3↑` take the first 3 (drops the milliseconds)  
`100+` one hundred added to each (to pad zeros)  
`':'@1∘⍕¨` amend with a colon at the first character of the string representation of each  
`∊` **ϵ**nlist (flatten)  
`1↓` drop the first colon (and implicitly print to stdout)

`⎕DL 1` **D**e**l**ay one second

`→2` go to line number two

[APL (Dyalog Unicode)]: https://www.dyalog.com/
[TIO-jbnj0ecc]: https://tio.run/##SyzI0U2pTMzJT///qKM9uCS/oDyxJDnjf/GjtgmP@qY6enIZPmqb/KijS91K3cHwUceMR71TD60wNDDQNn7UNtFAwQyMDF2NH3UtAeJmsB7dYi4g7eKjYMj1qG2SEcjk/3CjAQ "APL (Dyalog Unicode) – Try It Online"