diff --git a/models/shipcloud_pickup.py b/models/shipcloud_pickup.py
index 89f52b2..90cffc4 100644
--- a/models/shipcloud_pickup.py
+++ b/models/shipcloud_pickup.py
@@ -49,9 +49,9 @@ class SCPickup(models.Model):
         for p in self.pickings:
             sc_ship_ids.append({'id': p.sc_shipment_id})
         sc_addr = build_sc_addr(self.address)
-        sc_earliest = self.earliest.astimezone().isoformat()
+        sc_earliest = fields.Datetime.from_string(self.earliest).astimezone().isoformat()
         _logger.info("earliest: %s -> %s" % (self.earliest, sc_earliest))
-        sc_latest = self.latest.astimezone().isoformat()
+        sc_latest = fields.Datetime.from_string(self.latest).astimezone().isoformat()
         sc_pickup = shipcloud.gen_pickup(sc_addr, sc_earliest, sc_latest, sc_ship_ids, self.carrier)
         # actually use the SC API to request the pickup
         api = self._shipcloud_api()