ODP bug with generated SQL script when using DateTime

Question

With EF5, I'm getting some really weird SQL scripts when dealing with DateTime.
THe follow script works fine.
var a = db.MOTOR_POOL_RESERVATION
.Where(o => o.DEPART_DT > new DateTime(2013, 1, 1))
.Select(o => o.RESERVATION_ID)
.ToList();
SELECT "Extent1"."RESERVATION_ID" AS "RESERVATION_ID"
FROM "MOTORPOOL"."MOTOR_POOL_RESERVATION" "Extent1"
WHERE ("Extent1"."DEPART_DT" > TO_TIMESTAMP('2013-01-01 00:00:00.000', 'YYYY-MM-DD HH24:MI:SS.FF'))
But as soon as I create DateTime with year, month or day values forming from a variable, then generated scripts become incorrect.
var year = 2013;
var month = 3;
var dt = new DateTime(year, month, 1);
var c = db.MOTOR_POOL_RESERVATION
.Where(o => o.DEPART_DT > dt)
.Select(o=>o.RESERVATION_ID)
.ToList();
see the date is treated a string.
SELECT "Extent1"."RESERVATION_ID" AS "RESERVATION_ID"
FROM "MOTORPOOL"."MOTOR_POOL_RESERVATION" "Extent1"
WHERE ("Extent1"."DEPART_DT" > '2013-03-01 00:00:00')
var b = db.MOTOR_POOL_RESERVATION
.Where(o => o.DEPART_DT > new DateTime(year, month, 1))
.Select(o => o.RESERVATION_ID)
.ToList();
same problem with this one.
SELECT "Extent1"."RESERVATION_ID" AS "RESERVATION_ID"
FROM "MOTORPOOL"."MOTOR_POOL_RESERVATION" "Extent1"
WHERE ("Extent1"."DEPART_DT" > '2013-03-01 00:00:00')

Answer 1

It turns out that the sql is valid since I'm using bind parameters.