There was another "regular" adjustment of the time which is generated/calculated from the Rover's filename code seconds of about 60sec. (MER-A on sol2177 and MER-B sol2164), because of their clock drifts on Mars. But about then there has also something strange happened on the MER Pancam Data Tracking Web Interface. The Sols have suddenly shifted back additonally by one Sol.

For MER-A (Spirit):
On Sol 2176 at 12:00:41 the first image of the first sequence got:
/oss/mera/ops/ops/surface/tactical/sol/2176/opgs/edr/pcam/2P319538492ERPB27MP2684L8M1.IMG

On the same Sol (as displayed) at 12:03:24 the first image got:
/oss/mera/ops/ops/surface/tactical/sol/2176/opgs/edr/pcam/2P319627465ERPB27MP2128L2M1.IMG

Now the strange thing is, the difference of the seconds from the two entries is 88973 what means more than one Sol apart - i.e. according the filename seconds in the entry at 12:03:24 it's already Sol 2177 not 2176 ...?!

The same for Opportunity:

On Sol 2168 12:27:40 there's only a single image with:
/oss/merb/ops/ops/surface/tactical/sol/2168/opgs/edr/ncam/1N320649305ETHABJKP1994L0M1.IMG

In the next entry that displays Sol 2169 11:44:57 there the first image got:
/oss/merb/ops/ops/surface/tactical/sol/2169/opgs/edr/pcam/1P320824190ERPABJKP2601L8M1.IMG

That's a difference of the two entries of 174885 seconds - what means two Sols (174885/88775=1.97sol), i.e. it's already 2170 and not 2169 as displayed.

Was that intended or has something gone wrong here?

I see your point.
I had a glimpse of this "issue" today when I looked for images from the last drive, supposed to be during sol 2174, and found them to be "executed" on sol 2173. MMB reported them on sol 2174.

It seems that the images are being "allocated" to the previous sol. If you see, for example, the sequencing plan for sols 2169-2171 the "unexpected sequence!!!" ids on a given sol correpond to those planned (and executed, I presume) on the next one.

2. What EDRs do we have on the ground from sol 2169, 2170, 2171?

Actual number of EDRs by sequence number and image type:

Sol Seq.Ver ETH ESF EDN EFF ERP Tot Description
----- -------- --- --- --- --- --- ---- -----------
02169 p0765.03 10 0 0 10 0 20 Unexpected sequence!!!!
02169 p1201.07 2 0 0 2 0 4 Unexpected sequence!!!!
02169 p1212.09 2 0 0 2 0 4 Unexpected sequence!!!!
02169 p1301.06 2 0 0 2 0 4 Unexpected sequence!!!!
02169 p1312.07 2 0 0 2 0 4 Unexpected sequence!!!!
02169 p1981.26 4 0 0 4 0 8 Unexpected sequence!!!!
02169 p2128.02 3 3 0 0 1 7 pancam_cal_targ_L257
02169 p2128.02 3 3 0 0 1 7 pancam_cal_targ_L257
02169 p2383.24 15 0 0 15 0 30 pancam_survey_SE_5x1_L257
02169 p2384.24 24 0 0 24 1 49 pancam_survey_NE_4x2_L257
02169 p2601.04 4 2 0 0 2 8 pancam_tau_L78R48
02169 p2601.04 4 2 0 0 2 8 pancam_tau_L78R48
02169 p2601.04 0 0 0 0 0 0 pancam_tau_L78R48
02169 p2633.03 4 2 0 0 2 8 pancam_late_tau_L58R48
02170 p0765.03 0 0 0 0 0 0 navcam_5x1_az_288_3_bpp
02170 p1201.07 0 0 0 0 0 0 front_haz_penultimate_1bpp_pri17
02170 p1212.09 0 0 0 0 0 0 front_haz_ultimate_2_bpp_pri15
02170 p1254.02 0 0 0 0 0 0 front_haz_fault_pri15_4bpp
02170 p1301.06 0 0 0 0 0 0 rear_haz_penultimate_1bpp_pri17
02170 p1312.07 0 0 0 0 0 0 rear_haz_ultimate_2_bpp_pri15
02170 p1354.01 0 0 0 0 0 0 rear_haz_fault_pri15_4bpp
02170 p1981.26 0 0 0 0 0 0 nav_2x1_rvraz_0_1_bpp_pri24
02170 p1994.05 1 0 0 0 0 1 Unexpected sequence!!!!
02170 p2601.04 4 2 0 0 2 8 Unexpected sequence!!!!
02170 p2619.10 57 2 0 0 2 61 Unexpected sequence!!!!
...

Yes, since then it seems all displayed data lag now one Sol behind.
Now, should we report this issue someone? And to whom?

The issue and the cause have been identified. Essentially, there is a tool in the MIPL pipeline that has begun to calculate day numbers incorrectly (an inexact algorithm was identified as causing the issue...basically, enough sols have finally passed such that the imprecision has accumulated to produced an error). There is *no* issue related to the NAIF files. MIPL is investigating a remedy.