It seems from the way you have described the question (using monthly calendars) and have marked the beginning of the period as Jan. 2018 and the end of the period as July 2018 you are considering the 6 months (generally referred to in 61.57) as a 6 month "block" of time beginning with Jan. 2018 and ending July 2018.
Let me explain what I think is a better way of calculating whether or not you are current to act as PIC under IFR in accordance with 61.57. (for simplicity I will limit my answer to currency in an airplane (no simulators, FTD, glider, etc.)
Begin by looking at the date you want to fly IFR as PIC, say for example, Jun 5, 2018.
Then "look back" 6 calendar months beginning with the calendar month before [preceding] the month of the IFR flight you intend on taking on Jun 5. This would mean start your look back period from May.
Looking backward 6 calendar months beginning from May 2018 takes you back to the calendar month of December 2017 (the entire month is considered Dec 1 - Dec. 31).
In looking backward 6 months beginning May (May, April, March, February, January, December) you must have performed/logged the required currency maneuvers (e.g. 6 approaches, a hold, etc.) or else you won't be current for the IFR PIC flight on Jun 5.
As for when you need an Instrument Proficiency Check (IPC):
Determine the first calendar month, after looking back as described above, that you would not be legal to fly IFR PIC.
This will be calendar month number 1 of the 6 calendar months ("grace period") you have available to regain currency (without being PIC in IFR) and avoid an IPC.
For example, suppose you want to be PIC of an IFR flight on Jun 5th. You "look back" 6 calendar months beginning the count from May (as described above) and determine that you performed a Hold in Nov. 2017 and 2 IAPs in Dec. 2017 and 4 IAPs along with the other IFR currency requirements (e.g. tracking courses) in February 2018.
You note that the 6 calendar month "look back" period for a proposed Jun 5 flight involved a period beginning May 31, 2018, backwards to Dec. 1, 2017 and that you had met all currency requirements except for the Holding requirement, which was last done Nov. 2017 (not within the 6 calendar month look back time frame). Based on this scenario you would not be current to take the Jun 5 IFR PIC flight and would be "somewhere" in your 6 calendar month "grace period," per (61.57(d)).
As for when the "grace period" began (using the example above):
- You determined that on Jun 1, if you looked backwards at the 6 calendar months preceding [not counting] Jun (May 2018 backward thru Dec. 2017), your currency had lapsed for PIC IFR on May 31, 2018. Therefore, your 6 calendar month "grace period" (per 61.57(d)), would have begun on June 1 and run thru Nov. 30, 2018.
This regulation, 61.57, can be a bit confusing. However, if you consider that the 6 calendar months referred to in the various sections of the regulation are "rolling" (meaning that all calculations should be looking back for 6 calendar months preceding [not counting] the month of the IFR PIC flight under consideration), the regulation is a bit easier to understand.
Hope this helps.