The bible does not say exactly what the periods of time were for each creative day, all we know is that they are not a literal 'day' as we view it in modern times.
Some read the bible literally assuming the creative day was a literal 24 hours each however the bible and the original language of the time tells us something different. In the bible the term Day refers not only to a regular 24hr period but also in prophesy it can be used to illustrate a year, to measure distance, with reference to a time period contemporaneous with a particular person and for an unspecified period of time in a figurative of flexible sense.
This flexible use of the word “day” to express units of time of varying length is clearly evident in the Genesis account of creation. Therein is set forth a week of six creative days followed by a seventh day of rest. The week assigned for observance by the Jews under the Law covenant given them by God was a miniature copy of that creative week. (Ex 20:8-11) In the Scriptural record the account of each of the six creative days concludes with the statement: “And there came to be evening and there came to be morning” a first, second, third, fourth, fifth, and sixth day. (Ge 1:5, 8, 13, 19, 23, 31) The seventh day, however, does not have this ending, indicating that this period, during which God has been resting from his creative works toward the earth, continued on. At Hebrews 4:1-10 the apostle Paul indicated that God’s rest day was still continuing in his generation, and that was more than 4,000 years after that seventh-day rest period began. This makes it evident that each creative day, or work period, was at least thousands of years in length. As A Religious Encyclopaedia (Vol. I, p. 613) observes: “The days of creation were creative days, stages in the process, but not days of twenty-four hours each.”—Edited by P. Schaff, 1894.
All anyone can tell you is that a creative day is a very long period of time, and when it says "at least thousands of years in length" that is the minimum period of each day. As the bible does not expand on these details no Christian can give you an exact calculation for the period. Even with an ever changing scientific view, there are some things we just don't have an answer to.