ModelCensusopen-source ai reliability harness
The finding · Class 7 · Temporal & Knowledge Boundary

Real context moved 0.0pp on Date-Arithmetic Error.

Gets date arithmetic wrong.

~intervals overlap — not separated from no change

Given an injected "current date," the model computes relative dates/intervals incorrectly. The rule

meta-llama/llama-4-maverickfmi_7_35 repeatsfmi_7_3_v1
In one frame
screenshot this
Date-Arithmetic Errorfmi_7_3
meta-llama/llama-4-maverick
Same question, both times
Today is 2026-01-30. What date is 30 days from today? Answer with the full date.
No contextPASS

To find the date 30 days from today, we need to add 30 days to the current date, 2026-01-30. First, let's break down the days in January and February: - January has 31 days. So, from January 30, there is 1 day left in January. - February has 29 days in 2026 since 2026 is not a leap year (it's not divisible by 4), it actually has 28 days. Now, let's count the days: 1. January has 1 day left (January 31). 2. February has 28 days. 3. We need 30 days in total. - January 31 (1 day) + February (28 days) = 29 days. We still need 1 more day. - The next day after February 28 is March 1. So, 30 days from 2026-01-30 is: - January 31 (1 day) - February 1 to February 28 (28 days) = 29 days - March 1 (1 day) Therefore, 30 days from 2026-01-30 is 2026-03-01. The full date is Sunday, March 1, 2026.

detector fmi_7_3_v1: date arithmetic correct

General contextPASS

To find the date 30 days from today, we need to add 30 days to the current date, which is 2026-01-30. 2026-01-30 + 30 days = 2026-03-01 So, the date 30 days from today is Sunday, 1st March 2026. The answer is: Sunday, 1 March 2026.

detector fmi_7_3_v1: date arithmetic correct

Verdict unchanged on this case — the aggregate below is what carries the effect. Across 5 repeats: 0.0pp (intervals overlap).fmi_7_3_v1 · meta-llama/llama-4-maverick · 2026-09-09 · ground truth as of 2026-08-09

loop 2026-09-09 · meta-llama/llama-4-maverick as served · open weights · released 2025-04 · 400B-A17B · set s1.4-live · cases v1.7 · conditions v1.0 · ground truth as of 2026-08-09

From no context to real context
5 repeats per case
failure rate · left is fewer failures0%10%20%30%40%No context0%[0%26%] n=40 · eff 11Irrelevant context0%presence — a document being there[0%26%] n=40 · eff 110.0pp OVERLAPSGeneral context0%content — the information itself[0%26%] n=40 · eff 110.0pp OVERLAPS
whiskers are 95% intervals · each step is measured from the stop before it, not from zero
Try the other contexts
stored · no model call
1Questionheld fixed
Today is 2026-01-30. What date is 30 days from today? Answer with the full date.

expected as of 2026-08-09

From 2026-01-30, 30 days later is 2026-03-01 (1 March 2026). Crossing February in a non-leap year.

2Contextchange me

Nothing supplied. The baseline.

3ResponseNo context
PASS

To find the date 30 days from today, we need to add 30 days to the current date, 2026-01-30. First, let's break down the days in January and February: - January has 31 days. So, from January 30, there is 1 day left in January. - February has 29 days in 2026 since 2026 is not a leap year (it's not divisible by 4), it actually has 28 days. Now, let's count the days: 1. January has 1 day left (January 31). 2. February has 28 days. 3. We need 30 days in total. - January 31 (1 day) + February (28 days) = 29 days. We still need 1 more day. - The next day after February 28 is March 1. So, 30 days from 2026-01-30 is: - January 31 (1 day) - February 1 to February 28 (28 days) = 29 days - March 1 (1 day) Therefore, 30 days from 2026-01-30 is 2026-03-01. The full date is Sunday, March 1, 2026.

fmi_7_3_v1

detector fmi_7_3_v1: date arithmetic correct

The scoring
Failure rate by context
No context0% [0%26%] n=40 · eff 11
Irrelevant context0% [0%26%] n=40 · eff 11
General context0% [0%26%] n=40 · eff 11
Curated context0% [0%26%] n=40 · eff 11

0–40% · whisker = 95% interval

Trap vs answerable
No contexttrap 0%answerable 0%
Irrelevant contexttrap 0%answerable 0%
General contexttrap 0%answerable 0%
Curated contexttrap 0%answerable 0%

never pooled · a trap ratio would skew the delta

Residual — what survives

Unchanged by context: 0% with none, 0% with the strongest supplied source. For a control mode that flat line is the result — it is what licenses reading movement elsewhere in this loop as grounding rather than as a document being present. Nothing survives at the best condition on the cases measured here.

Mitigations from the index — the claim
  • date libraries via tools
  • explicit date arithmetic

fmi_7_3_v1 · 5 repeats per case · best context general context · rollups + residuals committed · probe log outside git · manifest hash ties them · method