Chronometric Injection

Large language models can reason about time when time is written in the prompt, but the standard transformer interface provides no first-class input for elapsed wall-clock duration. This matters for interactive and agentic systems, where the same visible prompt may require different responses depending on whether seconds, hours, or days have passed. This paper studies whether a frozen-base-weight autoregressive language model can be conditioned on a continuous elapsed-time scalar without updating its base weights. We introduce chronometric injection (CI), a residual-stream conditioning channel that encodes elapsed seconds τ with sinusoidal and logarithmic features and injects the resulting vector into a frozen Qwen2.5-3B-Instruct model through zero-gated AdaLN-style FiLM projectors. The contribution is not a new modulation primitive, but a causal and mechanistic characterization of an elapsed-time channel inside an otherwise frozen language model. Linear probes show that log τ is unrecoverable at layer 0, becomes nearly perfectly recoverable after one transformer block, remains recoverable through the network, and collapses to chance when the FiLM gates are zeroed. Behavioral results are more limited: the original zero-shot Temporal Policy Switching test remains negative, while direct policy supervision makes hidden elapsed time usable for forced-choice action control under identical visible prompts, reaching 0.8709 ± 0.0303 hidden-only accuracy. Overall, CI is best understood as a traceable residual-stream channel for elapsed-time conditioning, not as evidence of autonomous time tracking, broad policy generalization, or superiority over prompt-injected timestamps.