First proven reinfection, 142 days after first infection:
https://twitter.com/VirusesImmunity/...90418168860674
However, that person was asymptomatic after reinfection. Unknown whether that means all reinfections will be asymptomatic or if this is just one of many possible outcomes. Also unknown if this person is contagious after reinfection or would suffer any chronic problems after reinfection.