Re: 1 second
Don't account for leap seconds and in a couple of years time you are 30+ seconds out which means that no TOTP system (like Google Authenticator, banking apps, etc.) will generate the right codes if they are using different clocks that do (e.g. in a smartphone).
No. FTA:
[Since 1972] To date, there have been 27 leap seconds added – when clocks show 23:59:60 rather than rolling over to 00:00:00 after 23:59:59. The other 10 seconds arrived as a bulk adjustment in 1972.
Even including the 10-second block in 1972, that's 37 seconds over 46 years, or 0.8 per year. Even if we round up to 1/year, it would take 30 years to be 30 seconds out. By then you're likely to have replaced any system you're using for OTP 3-6 times over.