Can LLMs Be Constrained to the Past? Improving Knowledge Cutoff through Recall-Based Prompting

Michiro Asai, Ailiang Lin, Yu Kishimoto, Takao Obi, Satoshi Kosugi, Kotaro Funakoshi, Manabu Okumura


Abstract
Prompted knowledge cutoff instructs a large language model (LLM) to act as if information beyond a specified cutoff date were unavailable. However, prior work mainly relies on direct-answer generation, which struggles when post-cutoff knowledge is not explicitly queried but is only causally related to the question. To address this limitation, we propose two recall-based prompting strategies: Self-Recall (SR), which asks the model to restate its cutoff constraint, and Question-Recall (QR), which requires the model to recall question-relevant information valid under the cutoff. Across three existing benchmarks, our methods outperform both direct-answer prompting and conventional step-by-step reasoning baselines, with particularly strong improvements on counterfactual questions. To investigate robustness across different cutoff settings, we further construct the Multi-cutoff Historical Event Benchmark (MHEB), which evaluates the same question under multiple cutoff years. Results show that knowledge cutoff performance varies with cutoff distance, while combining SR and QR consistently yields the best performance. Code and dataset are available at [https://github.com/isct-lrlab/MHEB](https://github.com/isct-lrlab/MHEB).
Anthology ID:
2026.emnlp-main.895
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Junyi Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
20622–20637
Language:
URL:
https://aclanthology.org/2026.emnlp-main.895/
DOI:
10.18653/2026.emnlp-main.895
Bibkey:
Cite (ACL):
Michiro Asai, Ailiang Lin, Yu Kishimoto, Takao Obi, Satoshi Kosugi, Kotaro Funakoshi, and Manabu Okumura. 2026. Can LLMs Be Constrained to the Past? Improving Knowledge Cutoff through Recall-Based Prompting. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 20622–20637, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Can LLMs Be Constrained to the Past? Improving Knowledge Cutoff through Recall-Based Prompting (Asai et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.895.pdf