Accurate timebases
Using the line voltage as your frequency reference has it's limitations. For a frequency counter with the line voltage as a base, it cannot possibly have more than a five-digit accuracy even at best. Line frequency is accurate for digital clock use for the long-term, not the short term. Over weeks, problems with line frequency are averaged out. You can have some short term hiccups that limit you to only two or three digit accuracy at best. Five-digit accuracy translates into about ±0.01% while 3-digit accuracy is more like ±1%. A digital line-referenced clock is no more accurate than the analog version.
You can get oscillator-on-a-chip ICs from lots of sources, in nearly any frequency you want, including the 32,768 Hz (32.768 KHz) mentioned which you can divide down with a 15-stage binary counter string. Another option is a 1 MHz oscillator divided down with six decade dividers. The problem with an oscillator-on-a-chip is that you can't fine-tune the frequency like you can with a "discrete" design where you can pad the crystal with a trimmer cap to set the frequency dead-on. The advantages of the oscillator-on-a-chip are the low cost and tremendous space savings over a discrete design.
Here's idea #4853 for deriving an accurate 1 pps: Use the guts from a quartz clock movement that provides 1 pps to the solenoid that drives the second hand around the dial. Just get rid of all the mechanics and use some simple circuitry to get the logic to interface to your application.
Dean