From the 9th of each month, or approximately the 9th. Daily numbers sometimes 'estimated average' between 8th, 9th, and 10th as these can vary widely -/+ 30. Rounded to nearest 10th. Server downtime excepted.
November 2011: (registered count is inaccurate here from 600 unremoved inactive accounts, but I'd estimate ~9050 users), 790 weekly, 440 daily
Feb 2012: 960 registered, 760 weekly, 420 daily
May 2012: 1100 registered, 790 weekly, 410 daily
Aug 2012: 1150 registered, 780 weekly, 410 daily
Nov 2012: 1080 registered, 740 weekly, 370 daily
Feb 2013: 1050 registered, 770 weekly, 340 daily
May 2013: 1050 registered, 710 weekly, 370 daily
Aug 2013: 1050 registered, 630 weekly, 340 daily
Nov 2013: 950 registered, 590 weekly, 300 daily
Feb 2014: 840 registered, 550 weekly, 310 daily
May 2014: 800 registered, 540 weekly, 270 daily
Aug 2014: 730 registered, 450 weekly, 220 daily
Nov 2014: 670 registered, 410 weekly, 210 daily
Feb 2015: 600 registered, 390 weekly, 190 daily
May 2015: 590 registered, 390 weekly, 180 daily
Aug 2015: 520 registered, 330 weekly, 170 daily
Nov 2015: 490 registered, 320 weekly, 160 daily
Feb 2016: 460 registered, 300 weekly, 170 daily
May 2016: 440 registered, 280 weekly, 170 daily
The long downtrend (except registered accounts which I attribute to email server issues first and marketing second) stopped around the time of the November and December announcements and code changes.
We were starting to hit into 130s, 140s, 150s in daily usage around September/October/November, peaking around 170s, with an exceptional 190 on October 24, 2015. Weekly was hitting lows of 300s, 310s, averaging 320, from a high of 340/330s in August (last 330 september 2, last 320 october 30).
December we maintained 300s, 310s, hitting 288 for new year's eve and day. December's daily ranged between 150-180. January recovered to 300 and maintained 300s. January's daily between 160-180. February maintained high 290s, low 300s. February's daily between 160-180. March hit 310 (first time since dec 4th@311 or early january@308) and maintained high 290s to low 310s. March's daily between 160-180. April maintained 290s weekly, 150-180 daily.