Spend Shiva Ossor b’Tamuz in the Southern Hemisphere, and Assoro b’Teves in the Northern hemisphere.
For Yom Kippur & Tisha b’Ov, go the most Western part of the earth, and minutes after the commencement of Yom Kippur & Tisha b’Ov respectively, step over the Jewish Date Line, to the most Eastern part of the earth, and you shall have already just concluded Yom Kippur & Tisha b’Ov in a matter of minutes.