Optimize _lp_time/_lp_time_analog

`_lp_time_analog`:
- fix variable leaks (add `local`)
- use arithmetic features of the shell (`local -i`, `(( ... ))`)
`_lp_time`:
- fix wrong usage of `echo -e`

Note that `_lp_time_analog` was not working with zsh (always shows midnight) and this is not changed.