Try using the following:

.cf-date-field-date,
.cf-date-field-time {
  display:inline-block;
}

.cf-date-field-time {
  margin-top:0px;
  margin-right:150px;
  float:right;
}

.cf-date-field-date input[type="text"],
.cf-date-field-time input[type="text"] {
  width:142px;
}

A few notes on this,

1. You have to float the Time field container otherwise error messages will cause it to shift down and out of alignment with the date field.
2. You have to set an appropriate width because the defaults are percentage based and will be way too small when you put them inline.
3. You have to remove the top margin from the Time field container because it has a top margin meant to separate it from the date field.
4. You need to set margin-right on the Time field container to get it closer to the date field because of the float.