As quoted from:
Shulchan HaMelech, a Kitzur Shulchan Aruch in 3 volumes as compiled by Maharan HaRav Shmuel Laniado z'al, 1923 with the supplement "Al HaShulchan" containing various opinions compiled by Ezra Basri, Chief Justice of the District Court, Jerusalem in 1992.
We would also like to dedicate this learning for the speedy and complete recovery of two people: our friends' 5-year-old son, Joseph Benjamin, son of Ireneusz Khrystof, diagnosed in April with ALL leukemia, and a longtime friend of the family, Frank, son of Joseph, having thyroid surgery soon. Please have them in mind when studying. If you would like updates on their progress, please let me know so I can tell you when I find out from either or both.
p. 30 Chapter Nine Al HaShulchan
4. The time from when zizit can be put on with a blessing in the morning is when one can differentiate (in the natural light) between the techelet (the bluish dye of the Chilazon fish mentioned in the Torah as part of the commandments of zizit, but unavailable nowadays according to most authorities. tr.) and white colors of the zizit. The Jerusalem minhag (custom) is to reckon this time as being one hour before sunrise. (Sh.Ar. 18:3, K. Hach 18)
Note from us: Please consult your own rabbi to find out what to do - these are for learning purposes only.