Document date and datetime field types in README

README.md

@@ -574,6 +574,26 @@ try {
 > **Note:** `StockKeepingUnit` and `QtyBasedPricing` have no standalone API endpoints.
 > Access them via `include` on `didGroups` and `capacityPools` respectively.
 
+## Date and Datetime Fields
+
+The SDK distinguishes between date-only and datetime fields:
+
+- **Datetime fields** — deserialized as `OffsetDateTime`:
+  - All `getCreatedAt()` methods — present on most resources
+  - Expiry fields: `Did.getExpiresAt()`, `DidReservation.getExpireAt()`, `Proof.getExpiresAt()`, `EncryptedFile.getExpireAt()`
+- **Date-only fields** — deserialized as `LocalDate`:
+  - `Identity.getBirthDate()`
+- **Date-only fields kept as strings** (`CapacityPool.getRenewDate()`, `DidOrderItem.getBilledFrom()`, `DidOrderItem.getBilledTo()`) — remain as `String`.
+
+```java
+Did did = client.dids().find("uuid").getData();
+System.out.println(did.getCreatedAt());   // 2024-01-15T10:00:00Z  (OffsetDateTime)
+System.out.println(did.getExpiresAt());   // null or 2025-01-15T10:00:00Z
+
+Identity identity = client.identities().find("uuid").getData();
+System.out.println(identity.getBirthDate());  // 1990-05-20  (LocalDate)
+```
+
 ## Enums
 
 The SDK provides enum classes in `com.didww.sdk.resource.enums`:

src/main/java/com/didww/sdk/resource/CapacityPool.java

@@ -5,7 +5,6 @@
 import com.github.jasminb.jsonapi.annotations.Type;
 import lombok.Getter;
 
-import java.time.LocalDate;
 import java.util.List;
 
 @Type("capacity_pools")
@@ -17,7 +16,7 @@ public class CapacityPool extends BaseResource {
     private String name;
 
     @JsonProperty(value = "renew_date", access = JsonProperty.Access.WRITE_ONLY)
-    private LocalDate renewDate;
+    private String renewDate;
 
     @JsonProperty("total_channels_count")
     private Integer totalChannelsCount;

src/main/java/com/didww/sdk/resource/EncryptedFile.java

@@ -17,9 +17,6 @@ public class EncryptedFile extends BaseResource {
     @JsonProperty(value = "expire_at", access = JsonProperty.Access.WRITE_ONLY)
     private OffsetDateTime expireAt;
 
-    @JsonProperty(value = "created_at", access = JsonProperty.Access.WRITE_ONLY)
-    private OffsetDateTime createdAt;
-
     public void setDescription(String description) {
         this.description = markDirty("description", description);
     }