In any case, blood in the dog's stool should not be taken lightly and you should always take him or her to the vet as soon as possible. In the meantime, you can feed them white rice with a little garlic or garlic powder mixed in, boiled potatoes, green beans, or a little boiled chicken. When there is blood in a dog's stool. Yeah, it can be quite a scare, but when there is blood in a dog's stool and it doesn't always mean a trip to the emergency clinic.
If that's a valid date/time entry then excel simply stores it as a number (days are integers and the time is the decimal part) so you can do a simple subtraction. I'm not sure if 7/6 is 7th June or 6th July, assuming the latter then it's a future date so you can get the difference in days with. =INT(A1-TODAY()).
Time information in text strings is ignored, as you can see in rows 6 and 8 above. To convert text values containing both dates and times, use the VALUE function. If the year is omitted in a text date, Excel's DATEVALUE will pick the current year from your computer's system clock, as demonstrated in row 4 above.