The midpoint is Richburg, South Carolina. Columbia, SC and Charlotte, NC are in the same time zone (EDT). The best city between Charlotte, North Carolina and Columbia, South Carolina to meet is Rossville, South Carolina. The city located midway between Charlotte, North Carolina and Columbia, South Carolina is Beckhamville, South Carolina.
If you're looking for a meeting place or a good stopover half an hour or half way between Columbia and Charlotte, you can go to Binghamtown, South Carolina, which is almost an hour north of Columbia or almost an hour south of Charlotte.