is there a 'best day' for repotting a root bound house plant?
HA ha, sussexman you crack me up! You're always good for the one-liners, but now one-worders? Excellent! Just like the difference between a novel and a poem. Except that "yesterday" the moon is in Aries, not good.
Seriously though, the answer is best days are August 21st and 22nd. Second choice is 24th & 25th.
You can follow any of the gardening by the moon tasks for houseplants. You want the emphasis on root growth so do this after full moon (not after new moon). Pick a day for planting-transplanting-grafting when the moon is in the signs of either Cancer, Scorpio or Pisces as 1st choice. 2nd choices are Taurus, Virgo, or Capricorn.
SO Full Moon was the 13th, tomorrow is last quarter, and New is on the 28th.
Moon is in Taurus thru tomorrow, so NOW would give the roots time before the New moon.
Else you have the 24th & 25th, moon in Cancer.
NOTE: On the Almanac's calendar pages there is a column on the far right for Moon Place; do not go by that as it is the Astronomical Place. Use the chart on 2011 Almanac's page 230.