Add timestamps to conversation context

Feature Request

Add timestamps to messages and tool calls in the conversation context, so Claude can reason about when things happened.

Use Case

• "What did I work on yesterday?" — in a long-running or resumed session, Claude has no way to tell which messages happened when
• "How long ago did that build fail?"
• "How long has this command been running?"
• Whether a tool result (e.g., git status) is stale after a long session

Currently, Claude has no timestamps in its context — only the current date from a system reminder. It cannot tell when individual messages, tool calls, or user inputs occurred.

Proposal

Include timestamps (at least date + time) on:

• User messages
• Assistant messages
• Tool call results

Trade-offs

Timestamps add tokens to the context window, but the cost per message is small (~10 tokens) relative to the value they unlock.