Actually, you can. If you pass a real to datetime it will return the correct result:
sqlite> select typeof(cast(julianday('now') as real));
real
sqlite> select datetime(cast(julianday('now') as real));
2016-02-23 00:43:37
This is because datetime (the time functions) accept a string of the format
xxxxxx.xxxxxx and assume (unless the modifier 'unixepoch' is applied) that it
represents a julianday value.
