I figured it out. In RTKCONV, Click Options. Near the bottom of page where it indicates “Receiver Options” Enter “-TADJ=1.0” without the quotes, but in caps (it IS case sensitive). This will put time stamps on exact 1.0 second boundaries and properly tweak whatever needs to be tweaked (i.e. not just re-label a time stamp) I got this from an article on rtklibexplorer here: Using U-blox receiver options in RTKLIB – rtklibexplorer