+(: rfc3339->epoch (-> String (Option Nonnegative-Integer)))
+(define rfc3339->epoch
+ (let ([re (pregexp "^([0-9]{4})-([0-9]{2})-([0-9]{2})T([0-9]{2}):([0-9]{2})(:([0-9]{2}))?(\\.[0-9]+)?(Z|([+-])([0-9]{1,2}):?([0-9]{2}))?$")])
+ (λ (ts)
+ (match (regexp-match re ts)
+ [(list _wholething yyyy mm dd HH MM _:SS SS _fractional tz-whole tz-sign tz-HH tz-MM)
+ (let*
+ ([tz-offset
+ (match* (tz-whole tz-sign tz-HH tz-MM)
+ [("Z" #f #f #f)
+ 0]
+ [(_ (or "-" "+") (? identity h) (? identity m))
+ (let ([h (string->number h)]
+ [m (string->number m)]
+ ; Reverse to get back to UTC:
+ [op (match tz-sign ["+" -] ["-" +])])
+ (op 0 (+ (* 60 m) (* 60 (* 60 h)))))]
+ [(a b c d)
+ (log-warning "Impossible TZ string: ~v, components: ~v ~v ~v ~v" tz-whole a b c d)
+ 0])]
+ [ts-orig ts]
+ [local-time? #f]
+ [ts-epoch (find-seconds (if SS (string->number SS) 0)
+ (string->number MM)
+ (string->number HH)
+ (string->number dd)
+ (string->number mm)
+ (string->number yyyy)
+ local-time?)])
+ (+ ts-epoch tz-offset))]
+ [_
+ (log-error "Invalid timestamp: ~v" ts)
+ #f]))))