Add timehashes to nip 52 (#1752)

Co-authored-by: Jon Staab <shtaab@gmail.com>

2 files changed, 3 insertions, 4 deletions

diff --git a/52.md b/52.md
index 0b69007..060b38f 100644
--- a/52.md
+++ b/52.md
@@ -95,6 +95,7 @@ Aside from the common tags, this also takes the following tags:
 * `end` (optional) exclusive end Unix timestamp in seconds. If omitted, the calendar event ends instantaneously.
 * `start_tzid` (optional) time zone of the start timestamp, as defined by the IANA Time Zone Database. e.g., `America/Costa_Rica`
 * `end_tzid` (optional) time zone of the end timestamp, as defined by the IANA Time Zone Database. e.g., `America/Costa_Rica`. If omitted and `start_tzid` is provided, the time zone of the end timestamp is the same as the start timestamp.
+* `D` (required) the day-granularity unix timestamp on which the event takes place, calculated as `floor(unix_seconds() / seconds_in_one_day)`. Multiple tags SHOULD be included to cover the event's timeframe.
 
 ```yaml
 {
@@ -113,6 +114,7 @@ Aside from the common tags, this also takes the following tags:
     // timestamps
     ["start", "<unix timestamp in seconds>"],
     ["end", "<unix timestamp in seconds>"],
+    ["D", "82549"],
 
     ["start_tzid", "<IANA Time Zone Database identifier>"],
     ["end_tzid", "<IANA Time Zone Database identifier>"],
@@ -203,10 +205,6 @@ The list of tags is as follows:
 }
 ```
 
-## Unsolved Limitations
-
-* No private events
-
 ## Intentionally Unsupported Scenarios
 
 ### Recurring Calendar Events
diff --git a/README.md b/README.md
index 2e11906..c094d47 100644
--- a/README.md
+++ b/README.md
@@ -348,6 +348,7 @@ They exist to document what may be implemented by [Nostr](https://github.com/nos
 | `A`               | root address                         | relay URL                       | [22](22.md)                                        |
 | `c`               | commit id                            |                                 | [34](34.md)                                       |
 | `d`               | identifier                           | --                              | [01](01.md)                                        |
+| `D`               | day                                  | --                              | [52](52.md)                                        |
 | `e`               | event id (hex)                       | relay URL, marker, pubkey (hex) | [01](01.md), [10](10.md)                           |
 | `E`               | root event id                        | relay URL                       | [22](22.md)                                        |
 | `f`               | currency code                        | --                              | [69](69.md)                                        |